Methods and Apparatus for Three-Dimensional Printed Composites Based on Folded Substrate Sheets

ABSTRACT

A three-dimensional object comprises substantially planar or flat substrate layers that are folded and stacked in a predetermined order and infiltrated by a hardened material. The object is fabricated by positioning powder on all or part of multiple substrate layers. On each layer, the powder is selectively deposited in a pattern that corresponds to tiles that each have a slice of the object. For each slice, powder is deposited in positions that correspond to positions in the slice where the object exists, and not deposited where the object does not exist. The tiles of each substrate layer are folded and aligned in a predetermined order. Multiple folded substrate layers mat be combined into a single stack. The powder is transformed into a substance that flows and subsequently hardens into the hardened material in a spatial pattern that infiltrates positive regions, and does not infiltrate negative regions, in the substrate layers.

RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application Ser.No. 62/243,590, filed Oct. 19, 2015, the entire disclosure of which isherein incorporated by reference.

This application is also a continuation-in-part of co-pending U.S.patent application Ser. No. 14/835,685, filed Aug. 25, 2015, the entiredisclosure of which is herein incorporated by reference, which is acontinuation of PCT International Application Ser. No.PCT/US2014/018806, filed Feb. 26, 2014, the entire disclosure of whichis herein incorporated by reference, which claims the benefit of U.S.Provisional Application Ser. No. 61/769,724, filed Feb. 26, 2013, theentire disclosure of which is herein incorporated by reference. U.S.patent application Ser. No. 14/835,685 is also a continuation-in-part ofco-pending U.S. patent application Ser. No. 13/582,939, filed Nov. 2,2012, the entire disclosure of which is herein incorporated byreference, which is a 371 of PCT/US12/52946, filed Aug. 29, 2012, theentire disclosure of which is herein incorporated by reference, whichclaims the benefit of U.S. Provisional Application Ser. No. 61/528,537,filed Aug. 29, 2011, the entire disclosure of which is hereinincorporated by reference.

This application is also a continuation-in-part of co-pending U.S.patent application Ser. No. 14/835,690, filed Aug. 25, 2015, the entiredisclosure of which is herein incorporated by reference, which is adivisional of PCT International Application Ser. No. PCT/US2014/018806,filed Feb. 26, 2014, the entire disclosure of which is hereinincorporated by reference, which claims the benefit of U.S. ProvisionalApplication Ser. No. 61/769,724, filed Feb. 26, 2013, the entiredisclosure of which is herein incorporated by reference. U.S. patentapplication Ser. No. 14/835,690 is also a continuation-in-part ofco-pending U.S. patent application Ser. No. 13/582,939, filed Nov. 2,2012, the entire disclosure of which is herein incorporated byreference, which is a 371 of PCT/US12/52946, filed Aug. 29, 2012, theentire disclosure of which is herein incorporated by reference, whichclaims the benefit of U.S. Provisional Application Ser. No. 61/528,537,filed Aug. 29, 2011, the entire disclosure of which is hereinincorporated by reference.

This application is also a continuation-in-part of co-pending U.S.patent application Ser. No. 13/582,939, filed Nov. 2, 2012, the entiredisclosure of which is herein incorporated by reference, which is a 371of PCT/US12/52946, filed Aug. 29, 2012, the entire disclosure of whichis herein incorporated by reference, which claims the benefit of U.S.Provisional Application Ser. No. 61/528,537, filed Aug. 29, 2011, theentire disclosure of which is herein incorporated by reference.

FIELD OF THE TECHNOLOGY

The present invention relates to three-dimensional fabrication.

BACKGROUND

Three dimensional printing can be seen as largely a materials problem.One of the limitations of current methods is a limited materials paletteand slow build speeds.

These and other limitations of the prior art are avoided by amethodology known as Composite-Based Additive Manufacturing (CBAM). CBAMis described in full in co-pending U.S. patent application Ser. No.13/582,939, filed Nov. 2, 2012, Ser. No. 14/835,690, filed Aug. 25,2015, and Ser. No. 14/835,685, filed Aug. 25, 2015, each of which areincorporated fully herein by reference.

SUMMARY

In exemplary implementations, this invention comprises methods andapparatus for fabricating a 3D object. The object is made, at least inpart, of a layered composite material. For example, the compositematerial may comprise carbon fiber substrate layers joined by a hardenedthermoplastic or thermoset.

In exemplary implementations of this invention, a 3D object is formedlayer by layer, as follows: Thermoplastic powder (or thermosettableplastic powder) is selectively deposited on one layer of substrate, thenon a second layer of substrate, then on a third, and so on.

The powder may comprise polyethylene and the substrate layers maycomprise woven or nonwoven sheets of polylactic acid (PLA). However, avariety of materials may be used for the powder and substrate,respectively, and the substrate need not be either woven or fibrous. Ina preferred embodiment, the substrate is carbon fiber or other similarmaterials that will be apparent to one of skill in the art of theinvention.

In some implementations of this invention, in order to produce the 3Dobject, thermoplastic powder is selectively applied to some, but notall, regions of each carbon fiber substrate layer, respectively. Thepowder is then melted. The molten material infiltrates or coats at leastsome regions of the layers, cools and hardens. The hardened materialconnects or fuses together the substrate layers.

A computer processor may control the selective deposition of the powder,based on a CAD model of the 3D object. The CAD model is divided intothin sections or “slices”. On each substrate layer, the powder isdeposited only in some areas, and not in others. The pattern in whichthe powder is selectively deposited on each substrate layer,respectively, corresponds to a positive image of one of the slices. Thatis, for each slice of the 3D object: (a) powder is deposited inpositions that correspond to positions in the slice where the 3D objectexists, and (b) powder is not deposited in positions that correspond topositions in the slice where the 3D object does not exist.

In other implementations of this invention, thermoplastic powder isdeposited in an unselective manner (flooded) onto the substrate layers.Then the flooded powder is selectively melted (e.g., melted in some butnot all areas).

To build up the 3D object layer by layer, the substrate layers arealigned with each other and placed one on top of one another. Alignmentof the substrate layers may include folding a single substrate layeronto itself one or more times, which may be in accordance with apredetermined order for creating the three-dimensional object. Whenmultiple folded substrate layers are used, the folded layer stacks arealigned with each other and placed one on top of one another. This mayalso be in accordance with a predetermined order for creating thethree-dimensional object

Heat is applied (or heat and pressure are applied) to the powder andsubstrate, causing the powder, not the substrate, to melt. The resultingmolten material coats the substrate. The molten material then cools andsolidifies. The solidified material holds adjacent layers of substratetogether. For example, the solidified material may bridge betweendifferent layers of the substrate. In this manner, a part of each layerof substrate is coated by this solidified material. In someimplementations, heat and pressure are applied once per layer. In otherimplementations, they are applied less frequently (e.g., once every twolayers, or less frequently).

In exemplary implementations of this invention, once the thermoplasticplastic has hardened, part of each substrate layer has been infiltratedor coated by the hardened material and another part (the “excessregion”) of each substrate layer has not been infiltrated or coated bythe hardened material. The excess region of each layer (which was notinfiltrated by the hardened material, e.g. the hardened thermoplastic)is then removed.

At least once in the process (e.g., at the end of the process), excesssubstrate is removed. The excess substrate is that portion of eachsubstrate layer that is not coated by the solidified material. Inexemplary implementations of this invention, the excess region may beremoved, at least partially, by non-mechanical means, e.g., bydissolution or chemical degradation. Removal of the excess substrate maybe accomplished, for example, by dissolution or polymer degradation. Inthose cases, the solvent or degrading agent employed depends on thesubstrate material that is employed. For example, if the substratecomprises PLA fabric, then potassium hydroxide in methanol may be usedto dissolve the excess (uncoated) portion of each substrate layer. Or,for example, if the substrate comprises polyvinyl alcohol (PVOH) fabric,then water may be used to dissolve the excess substrate.

The excess region may also be removed by mechanical means, such as, butnot limited to, abrasion, including abrasive blasting. For example, in aprototype of this invention, the excess region is removed by glass beadblasting. As used herein, the term “abrasion” includes abrasiveblasting.

In exemplary implementations of this invention, a broad range ofabrasive blasting techniques and materials may be employed for thepurpose of removing the excess region. For example, the abrasivematerial used in the abrasive blasting may comprise, but is not limitedto, any one or more of the following: garnet, glass beads, glass grit,aluminum oxide, silicon carbide, carborundum, ceramic shot, ceramicgrit, steel shot, steel grit, cut wire, copper shot, aluminum shot, zincshot, other metallic abrasives, copper slag, nickel slag, magnesiumsulfate, kieserite, staurolite, sodium bicarbonate, dry ice, plasticabrasive, or crushed nut shells. Also, for example, the abrasive mediummay be propelled by a pressurized fluid (e.g., air or water) or by amoving object (e.g., a rotating wheel).

The abrasion methods and apparatus used to remove the excess region arenot limited to abrasive blasting. In illustrative implementations ofthis invention, other methods and apparatus for abrasion may be used,including, but not limited to, bristle blasting, rotary brushes, wirebrush, sandpaper, emery paper, belt sanders, or files.

In exemplary implementations of this invention, the excess region may beremoved in other mechanical ways, besides abrasion. For example, saws,drill bits, burrs, awls, scrapers, dental tools (e.g., periodontalscalers or periodontal curettes), thread, and abrasive thread may beemployed for this purpose.

The desired 3D object is defined by that portion of layers where thepowder has been selectively deposited and melted (i.e., that portionwhich is coated by the solidified material once the melted powder coolsand solidifies).

Alternatively, in some implementations, no powder is used. Instead, forexample, a liquid (e.g., a liquid thermoplastic or liquid thermosettingpolymer) may be selectively deposited on a layer of substrate. Thesubstrate layer may comprise carbon fiber. The liquid may comprise, forexample, an epoxy resin, UV curable resin or acrylic resin. The liquidmay infiltrate or coat the substrate layers, and then harden or cure,fusing together layers of substrate. The excess portion of the substratelayer (which has not been infiltrated or coated by the liquid) may beremoved, as described above. A composite material may be fabricated,layer by layer, in this manner. For example, the composite material mayinclude carbon fiber.

The entire process (or parts of the process) may be automated andcomputer controlled. For example, one or more of the following may beautomated and computer controlled: the selective deposition of powder,removal of excess powder, feeding of substrate sheets, heating andpressing, and removal of excess substrate.

The 3D object that is printed comprises a composite material (thesolidified plastic and the substrate that it coats). In one aspect, athree-dimensional article of manufacture according to the inventioncomprises a plurality of substrate layers that are folded and stacked ina predetermined order for creating the article and are infiltrated orcoated by, and bound together by, a hardened material, wherein eachsubstrate layer is a sheet-like structure that is substantially planaror flat and is made from materials that can be abraded, abrasivelyblasted, or chemically removed. In some embodiments, the substrate layermaterials may comprise carbon fibers, ceramic fibers, polymer fibers,glass fibers, and/or metal fibers.

This invention has numerous advantages over existing technology. Amongother things, in exemplary embodiments: First, it can be used with awide variety of materials for the powder, substrate and solvent ordegrading agent. Second, it produces composite materials, and thus canprint 3D objects with highly desirable material properties, such as highstrength and low weight. Third, it can fabricate objects at a very rapidpace, in some implementations. Fourth, it can also produce much largerobjects than present technology and the parts can be colored ordecorated.

In particular exemplary implementations, the invention can use carbonfiber (together with other materials) to fabricate composite parts thatare strong, light and have better performance than metals in manyrespects. The composite materials that are produced have materialproperties that are better than many homogenous materials. Since theprocess can use conventional thermal inkjet heads, the cost of themechanism is substantially reduced and the process is much faster thanexisting 3D printing methods.

The above description of the present invention is just a summary. It isintended only to give a general introduction to some illustrativeimplementations of this invention. It does not describe all of thedetails of this invention. This invention may be implemented in manyother ways, including with thermosettable powder.

BRIEF DESCRIPTION OF THE DRAWINGS

Other aspects, advantages and novel features of the invention willbecome more apparent from the following detailed description of theinvention when considered in conjunction with the accompanying drawingswherein:

FIG. 1A is a high-level flow chart of steps used to manufacture a 3Dobject, in an exemplary embodiment of this invention.

FIG. 1B is a high-level flow chart of steps used to manufacture a 3Dobject, in another exemplary embodiment of this invention.

FIG. 1C is a high-level flow chart of steps used to manufacture a 3Dobject, in another exemplary embodiment of this invention.

FIG. 2A shows an exemplary substrate layer useable in the presentinvention.

FIG. 2B is a magnified view of part of the same substrate layer, showingthreads in the substrate layer.

FIG. 2C is a magnified view of part of one of the threads, showingfibers in the thread.

FIG. 2D depicts the exemplary substrate layer of FIGS. 2A-C with adeposited ring of liquid.

FIG. 2E is a cross-sectional view of the exemplary substrate layer ofFIGS. 2A-C, showing thermoplastic powder adhering to liquid that hasbeen selectively deposited on the substrate.

FIG. 3 is a cross-sectional view of multiple substrate layers boundtogether by solidified thermoplastic, after thermoplastic powder hasmelted, coated a portion of the substrate layers, and cooled.

FIG. 4 is a cross-sectional view of the multiple substrate layers ofFIG. 3, after excess substrate has been removed.

FIG. 5 shows apparatus used to selectively deposit liquid, to whichpowder adheres, in an illustrative implementation of this invention.

FIG. 6 is a high-level block diagram of processors, in an illustrativeimplementation of this invention.

FIGS. 7A-D to 11 illustrate a prototype of this invention. In theexample shown in FIGS. 7A-D to 11, a ring torus is being fabricated.

FIG. 7A shows a pattern that has been inkjet-printed on a substratelayer. The pattern comprises a 4×3 matrix. In each tile of the matrix,respectively, a different cross-sectional “slice” of the ring torus hasbeen printed by the inkjet printer.

FIG. 7B depicts a substrate layer similar to that of FIG. 7A, with thegrid defined by laser cut perforations at the grid lines.

FIG. 7C depicts the substrate layer of FIG. 7B, with some of the gridlines cut to enable folding.

FIG. 7D depicts the substrate layer of FIGS. 7B and 7C, folded to stackthe tiles in the correct order.

FIG. 8 shows a compressive device, after the substrate tiles (layers)have been placed in it, stacked one on top of the other in thecompressive device. The tiles are aligned by inserting two registrationpins of the compressive device into the two registration holes of eachtile, respectively.

FIG. 9 shows the compressive device of FIG. 8, after all substratelayers with all of the “slices” of the ring torus have been insertedinto it, assembled so that springs in the compressive device press thesubstrate layers together.

FIG. 10 shows the layers of substrate, fused together into a rectangularcuboid.

FIG. 11 shows the exemplary ring torus that remains after excesssubstrate in the rectangular cuboid of FIG. 10 has been removed.

FIG. 12A shows a grain of powder that microencapsulates a liquid.

FIG. 12B shows a powder mixture that comprises two types of grains:first, a completely solid grain; and second, a grain that comprises asolid outer layer that encapsulates a liquid.

FIG. 13 is a block diagram that shows a processor that controls multiplecomponents of an apparatus for fabricating a 3D object.

FIG. 14A is a high level flow chart of steps in an exemplaryimplementation of this invention.

FIG. 14B is a high level flow chart of steps in another exemplaryimplementation of this invention.

FIG. 15 shows part of an abrasive blasting apparatus as it starts toabrade the excess region from a stack of carbon fiber layers.

FIG. 16 is a photograph of a 3D object, comprising a carbon fibercomposite material, which was fabricated by a prototype of thisinvention.

FIGS. 17A-B depict an alternate embodiment in which a roll is perforatedevery X inches, printed, powdered, and then folded accordion-style.

The above Figures show all or part of illustrative embodiments of thisinvention, or of products of those embodiments, but may not show all ofthe details of individual embodiments of the invention.

DETAILED DESCRIPTION

In exemplary implementations of this invention, a 3D object is formedlayer by layer. Powder is selectively deposited on each layer. Thepowder is melted, so that it coats a portion of the substrate layer. Themelted powder then solidifies, bonding the layers of substrate together.The excess substrate that is not coated by the solidified material issubsequently removed. In a preferred embodiment, the substrate is carbonfiber and the excess substrate is removed by abrasion.

FIGS. 1A-1C are each flow charts of steps used to manufacture a 3Dobject according to three illustrative embodiments of this invention,respectively.

In the embodiment shown in FIG. 1A, thermoplastic powder is selectivelydeposited 105 on one layer of substrate, in a pattern that correspondsto a “positive image” of a “slice” of the 3D object that is beingprinted. This layer is aligned 110 on top of another layer of substrate,with the selectively deposited powder between them. Heat and pressureare applied 115 in order to melt the powder and cause the resultingmolten material to coat a portion of the respective layers and make thesubstrate layers adhere to each other. This may be done once each layer,or less frequently (e.g., once every two or three layers). When themolten powder cools, it solidifies. This process is repeated 120 untillayers corresponding to all of the “slices” of the desired 3D objecthave been added. The excess substrate (which is not coated by thesolidified material) is then removed 125, leaving the 3D object.

In the alternate embodiment shown in FIG. 1B, a printer is used to print130 a pattern of liquid on a substrate layer. The pattern defines a gridof “tiles.” A positive image of a different “slice” of a 3D object isprinted in each tile, respectively, of the printed pattern. The liquidmay be conventional ink of an inkjet printer, water, or another liquid.Thermoplastic powder is applied 135 to the substrate layer. The powderadheres to the liquid, and not elsewhere. The excess powder is removed140. The substrate layer is cut 145 in order to separate the tiles. Thetiles are placed 150 on top of another. This is repeated until tilesrepresenting all of the slices of the 3D object are placed on top ofeach other in the proper order. Heat and pressure are applied 155 to thetiles. This heats the thermoplastic powder and causes it to melt. Themolten material coats at least a portion of the substrate layers, cools,and solidifies. The solidified material fuses adjacent layers ofsubstrate together. Excess substrate (i.e., the uncoated portion of thesubstrate) is then removed 160.

In the alternate embodiment shown in FIG. 1C, a printer is used 165 toprint a pattern of liquid on a substrate layer. The pattern defines agrid of “tiles.” A positive image of a different “slice” of a 3D objectis printed in each tile, respectively, of the printed pattern. Theliquid may be conventional ink of an inkjet printer, water, or anotherliquid. Thermoplastic powder is applied 170 to the substrate layer. Thepowder adheres to the liquid and not elsewhere. The excess powder isremoved 175. The substrate layer is folded 180 in order to layer thetiles. Folding into layers is repeated 185 until tiles representing allof the slices of the 3D object are placed on top of each other in theproper order. Heat and pressure is applied 190 to the tiles. This heatsthe thermoplastic powder and causes it to melt. The molten materialcoats at least a portion of the substrate layers, cools, and solidifies.The solidified material fuses adjacent layers of substrate together.Excess substrate (i.e., the uncoated portion of the substrate) is thenremoved 195, leaving the 3D object.

In illustrative implementations of this invention, the 3D object isprinted in accordance with a computer 3D model of the object, created bya CAD program. For example, the CAD program may be a free-form NURBS(non-uniform rational basis spline) program, such as Rhinoceros®(available from McNeel North America, Seattle, Wash.), or, for example,the CAD program may be SolidWorks® (available from Dassault SystèmesSolidWorks Corp., Concord, Mass.).

On each substrate layer, powder is selectively deposited in a physicalpattern that corresponds to a “positive image” of a thin slice orsection of the 3D object. That is, for each slice of the 3D object: (a)powder is deposited in positions that correspond to positions in theslice where the 3D object exists, and (b) powder is not deposited inpositions that correspond to positions in the slice where the 3D objectdoes not exist.

Thin slices of the 3D CAD model may be created, for example, by startingwith a 3D model in STL file format and using the Slice Commander featureof netfabb® Studio software (available from netfabb GmbH, Parsberg,Germany) to create the thin slices.

Selective Deposition of Powder:

According to principles of this invention, the powder may be selectivelydeposited on substrate layers in many different ways.

EXAMPLE 1 Of Selective Deposit of Powder

First, powder may be selectively deposited on a substrate layer bymaking the powder adhere to a liquid, as follows: A liquid isselectively deposited on a substrate layer, so that some parts of thesubstrate layer are covered with liquid, and some are not. Then the sideof the substrate layer on which the fluid was deposited is flooded withpowder (e.g., the powder is poured on this side of the substrate layer).The powder adheres to the liquid. The excess powder (i.e., the powderthat is not adhering to the liquid) is removed. For example, this excesspowder may be removed by vacuuming. Or, for example, the substrate maybe flipped over, so that the excess powder falls off. Or the substratemay be turned upside down and flicked with a finger. The substrate mayalso be vibrated while the excess powder is removed, in order tofacilitate the removal.

In some cases, the liquid that is selectively deposited is water (or anaqueous solution that includes a material that slows the evaporation ofwater). For example, the material may be 2-pyrrolidinone. In othercases, it is a different liquid, such as an alcohol. For example, if thesubstrate is water sensitive (e.g. if the substrate is polyvinylalcohol, PVOH), then water may distort or dissolve the substrate. Inthat case, an alcohol may be used as the liquid that is selectivelydeposited. In some cases, to prevent the liquid that is selectivelydeposited from spreading or being excessively absorbed into thesubstrate, it is helpful to apply a surface energy modifier to thesubstrate, before selectively depositing the liquid. For example,Scotchguard® Fabric & Upholstery Protector (available from 3M, St. Paul,Minn.) may be sprayed or deposited on the substrate layer for thispurpose. Alternatively, other repellents or surface energy modifiers canbe used.

In this first example, a variety of methods may be used to dispense theliquid. For example, a thermal inkjet head or a piezoelectric inkjethead may be used to dispense the liquid. For example, the inkjet headmay comprise a HP45 cartridge, HP C 6602A cartridge, or HP51604Acartridge (available from Hewlett Packard Corp.) or a Lexmark® 50cartridge or Lexmark 60 cartridge. Alternatively, air pressure may beused to dispense the liquid (e.g., through a 0.005 inch nozzle obtainedfrom the Lee Company, Essex, Conn., part INZA650935K). If air pressureis used, the release of air or dispensing of liquid may be controlled bya solenoid valve.

EXAMPLE 2 Of Selective Deposit of Powder

The powder may alternatively be selectively deposited by flooding oneside of a layer of substrate with powder, then selectively heating theopposite side of the substrate with an appropriate device such as athermal print head. For example, a thermal print head from MitaniMicronics Co., Ltd., Tokyo, Japan may be used. In this approach, thethermal print head includes a high-resolution array of heating elements,which may be selectively turned on or off. In the areas that are heated,the powder melts and adheres to the substrate. The excess powder thathas not adhered is removed. Again, this may be done by vacuuming theexcess powder, or by flipping the substrate layer over. Again, vibrationmay be used to facilitate the removal of the powder. The thickness ofthe deposited powder can be controlled in this example implementation bydoctoring a precise thickness of powder on the substrate.

EXAMPLE 3 Of Selective Deposit of Powder

Alternatively, powder may be deposited using a selective depositiontechnique similar to that employed in xerographic printing. In thisapproach, an electrical charge is imparted to powder particles, whichare directed toward the substrate layer and then selectively adhere tosome portions of the substrate but not others due to electrostaticattraction or repulsion. The powder particles adhere to portions of thesubstrate that have an opposite electrical charge, or that are adjacentto a surface that has such a charge, and are repelled from portions ofthe substrate that have the same electrical charge or that are adjacentto a surface that has such a charge.

EXAMPLE 4 Of Selective Deposit of Powder

The powder may be alternatively deposited using a selective depositiontechnique similar to that employed in magnetographic printing. In thisapproach, powder selectively adheres to some portions of the substratelayer, but not others, due to magnetostatic interactions between thepowder and the substrate layer (or a surface adjacent to the substratelayer). For example, the powder may be a single component magnetictoner, or may comprise a colloidal suspension (e.g., a ferrofluid), ormay be a dual component toner. A variety of magnetic pigments, such asmagnetite (Fe₃O₄) or ferric oxide ((Fe₂O₃), may be used for the toner inthis approach.

General Observations on Selective Deposition of Powder:

In all of the above examples, the step of selectively depositing powdermay include a substep of directing solid powder toward the substratelayer in a non-selective manner. For example, this substep may compriseflooding the entire layer of substrate with powder. Or, for example, inthe xerographic or magnetographic examples, this substep may comprisesending electrically charged or magnetized powder toward the entiresubstrate layer.

This invention is not limited to the four examples of selectivedeposition described above, but may be implemented using any techniqueknown in the art to selectively deposit the powder.

In exemplary implementations, liquid is selectively dispensed in a 2Dpattern that corresponds to the slice that it is being printed for theparticular substrate layer. After the liquid is dispensed on thatsubstrate layer, the top of the substrate layer is then flooded withthermoplastic powder. The powder adheres to the liquid, but does notadhere to the portions of the substrate layer that are not covered withthe liquid. The excess powder is then removed. This may be done, forexample, by vacuuming the excess powder off, or by the simple expedientof flipping the substrate layer over.

Heat, Pressure:

In exemplary implementations of this invention, pressure and heat areapplied to the layers of substrate being fused, to melt the powder andto press the layers together. The pressure may additionally tend toforce the melted thermoplastic to coat the substrate.

For example, a hot stamp press may be used to apply heat and pressure.Or, for example, the substrate may be placed in a heated oven, whilepressure is applied with a clamp or other compressive device. In bothcases, once the powder melts, the pressure may tend to force the moltenmaterial to coat the substrate layers. In the case of oven heating, atacking iron may be used to tack the substrate layers together beforeinserting them into the oven.

In many implementations, the powder is caused to melt after it has beenselectively deposited: i.e., the melting occurs after the excess powderhas been removed.

However, if a thermal print head (with an array of heating elements) isused, then the melting is part of the process of selective deposition.The print head selectively heats portions of a substrate layer that hasbeen flooded (on the side of the substrate layer opposite from the printhead) with powder, so that, in the heated areas, the powder melts andadheres to the substrate. Excess powder is removed. Heat and pressureare then applied, causing the adhered material to melt (or to remainmolten) and to coat part of the substrate.

The molten material then cools and solidifies into a solid that coats aportion of the substrate layer. It also holds multiple substrate layerstogether.

For example, if the substrate is fibrous, the molten material may coatthese fibers. When the material solidifies, it continues to coat thesefibers.

How frequently the powder is melted and the pressure is applied mayvary. In some implementations, these steps occur once for each layer. Inother implementations, at least some of these steps occur lessfrequently. For example, heat and pressure may be applied only once forevery two layers of substrate, or once for every five layers ofsubstrate, etc.

Removal of Excess Substrate:

A portion of the substrate is not coated, because powder was not presentand melted in that area. That excess substrate is removed.

A variety of removal techniques may be employed for excess substrateremoval. In some embodiments, excess substrate is removed by one or moreof: dissolution, polymer degradation, mechanical abrasion, or melting.If dissolution or degradation is employed to remove excess substrate,the dissolution or degradation may be accelerated by agitating and/orheating the agent used for dissolution and/or degradation. For example,any of the following may be agitated or heated to speed the dissolutionor degradation: (a) sodium hydroxide or other alkali in aqueous solutionor in an alcohol (e.g., ethanol or methanol), (b) potassium hydroxide inan alcohol (e.g., methanol or in ethanol), (c) water, and (d)hydrochloric acid in aqueous solution. Agitation may be achieved, forexample, by ultrasound, a magnetic or paddle stirrer, shaking, or jetsof liquid. If mechanical abrasion is used, then it is advantageous touse a substrate material that can be easily removed by abrasion when notcoated. The object may be placed in a mechanical tumbler to facilitateabrasion.

This invention is not limited, however to the methods of removing excesssubstrate listed above. Other removal approaches may be employed whichrely on a difference in material properties of the substrate and thesolidified thermoplastic that causes the former to be more susceptiblethan the latter to the removal agent.

In some exemplary implementations, the removal of the excess substrateoccurs just once, at the end of the process. Alternatively, the removalof the excess substrate may occur more than once during the process.

Thermoplastic or Thermosettable Powder:

In exemplary implementations, a thermoplastic powder is used. Forexample, the powder may be Shaetti® SF 400 or Shaetti® Fix 1820thermoplastic powder (available from Shaetti America, Inc., Mooresville,N.C.) or another powder that melts, flows, and bonds under heat. Thethermoplastic powder may comprise a polyethylene or other polyolefin.Advantageously, polyethylene may have a lower melting point than thesubstrate, and may be impervious to many solvents, acids and otherchemicals that degrade plastics (and thus would not be affected if suchchemicals were used to remove excess substrate).

Alternatively, a thermosettable powder that melts and flows sufficientlyto coat the substrate may be used.

Substrate/Removal of Excess Substrate:

Depending on the particular implementation of this invention, differenttypes of substrates may be used, and, correspondingly, differentmaterials may be used to dissolve or degrade excess substrate. Table 1is a non-exhaustive list of some materials that may be used as the (1)substrate and (2) corresponding solvent or material for degradation.

TABLE 1 Substrates and Removal Agents Material used for removal ofexcess substrate (e.g., Substrate by dissolution or degradation)Polyethylene mixture comprising either: (1) alcohol and alkali (e.g.,terephthalate Everclear ® grain alcohol and sodium hydroxide) (the (PET)alcohol may comprise ethanol or methanol); or (2) methanol and potassiumhydroxide. polylactic acid (1) sodium hydroxide (in aqueous solution),or (PLA) (2) potassium hydroxide (in methanol or ethanol) (3) Strip-X ®Stripper*(available from W.M. Barr & Co., Memphis, TN) polyvinyl alcoholwater (PVOH) polyamide hydrochloric acid (nylon) water soluble waterpaper paper hydrochloric acid, or enzymes silk hydrochloric acidfiberglass hydrofluoric acid carbon fiber, abrasion fiberglass, ceramics*Strip-X ® Stripper contains acetone, methanol, methylene chloride,toluene, and xylene.

For example, PLA (available from Ahlstrom Chirnsdale Ltd., Chirnsdale,Scotland, U.K., and from C.L. Enterprises, Wenzhou, China) may be usedas the substrate.

In exemplary implementations, the substrate comprises a woven material.Alternatively, the substrate may comprise a non-woven textile. Forexample, non-woven PVOH (available from Freudenberg USA) may be used asa substrate. Also, for example, the non-woven substrate may comprise HV7841, HV 7801 or HV CTR2863A polyester, each available fromHollingsworth and Vose (East Walpole, Mass.), or may comprise A0514WHTpolyester, available from Freundenberg. Or, for example, the substratemay comprise paper or another cellulose-based or plant fiber-basedmaterial.

As noted in the table above, water-soluble paper may be used for thesubstrate. For example, the water soluble paper may be of the typedescribed in U.S. Pat. No. 3,431,166 (in which paper is reacted withalkali during manufacture). Or, for example, the paper may employpolyvinyl alcohol (PVOH) which is used to bind paper fibers together.The former type of water soluble paper may be obtained from AquasolCorporation (North Tonawanda, N.Y.), and the latter type may be obtainedfrom Hollingsworth and Vose Company (East Walpole, Mass.).

A problem with water-soluble paper is that it tends to swell whenexposed to water. This swelling may be reduced by using a high pressurewater jet, which tends to rapidly remove the paper that has been exposedto water, before the water can migrate into paper that has beenpartially coated with melted powder.

Alternatively, if ordinary paper (that is not water-soluble) is used asthe substrate, then excess paper may be removed by enzymes that digestpaper. For example, in a working prototype of this invention, the enzymecomplex Accellerase® 1500 from Genencor (a division of Danisco USA,Inc., Tarrytown, N.Y.) is used for that purpose. An advantage of thisapproach is that it lessens or avoids the swelling associated withsimply dissolving some types of water-soluble paper.

This invention is not limited to the substrate materials and solvents ordegrading agents listed in Table 1, but may also be implemented withother substrate materials, and solvents and degrading agents.

Among other things, different substances may be applied to orincorporated into the substrate layers in order to modify the absorptioncharacteristics or surface energy of the substrate. For example, thesubstrate's absorption characteristics may be modified in this way withrespect to a variety of liquids, such as melted powder, or liquidsolvent or degrading agent, or a liquid that is dispensed for the powderto adhere to. In some implementations, a sizing material that acts as afilter or a glaze may be used for this purpose. The use of Scotchguard®Fabric & Upholstery Protector (available from 3M, St. Paul, Minn.) orother repellents, such as those mentioned above, is an example ofapplying a substance that changes the absorption characteristics andsurface energy of the substrate layer.

Registration/Alignment:

In exemplary implementations of this invention, a registration/alignmentmechanism is employed to cause the layers of substrate to be alignedduring the 3D printing process. For example, guide posts in aregistration form may be inserted into guide holes in the substratelayers. Or, for example, a corner of each substrate layer may be pushedinto a guide corner, to align the layer with other layers. Or, forexample, a light sensor or camera may be employed to determine whethersubstrate layers are aligned. Alignment of the substrate layers mayinclude folding a single substrate layer onto itself one or more times.This invention is not limited to the specific alignment/registrationtechniques described herein, but may employ any type ofalignment/registration to align the substrate layers.

Substrate Layers:

FIG. 2A shows a substrate layer 201, in an illustrative implementationof this invention. FIG. 2B is a magnified view of part of the samesubstrate layer 201, showing woven threads (e.g., thread 203) in thesubstrate layer. FIG. 2C is a magnified view of part of thread 203,showing fibers (e.g., 205) in thread 203. In the example shown in FIGS.2A, 2B and 2C, the substrate is woven and fibrous. However, non-wovenfibrous substrates may be used instead. For example, the substrate maycomprise a composite, nonwoven material that includes threads, shortfibers, long fibers, and/or whiskers. Alternatively, the substrate maycomprise spherical particles, ellipsoidal particles, flakes, smallplatelets, or small ribbons, or particulates of any other suitableshape, which are joined together by a glue or other binding material.

FIG. 2D shows substrate layer 201, after applicator 213 has selectivelydeposited a circular ring of liquid 215 on the layer. Deposited liquid215 corresponds to a cross-sectional slice of the target 3D object(which, in this example, is a circular vase). For example, substratelayer 201 may comprise carbon fiber, and liquid 215 may comprise athermosetting polymer resin mixture or a thermoplastic polymer liquid.

Alternatively, the liquid employed may be any liquid suitable fordeposition by an applicator, e.g., by an inkjet head. For example, inthose cases where a thermoplastic powder is used, liquid may beselectively applied by an inkjet head to the substrate layer in adesired pattern, and then powder may be flooded onto the substrate, andadhere to the liquid in the desired pattern. FIG. 2E illustrates thisexample. FIG. 2E is a cross-sectional view of substrate 201 of FIGS.2A-C, showing thermoplastic powder 221 adhering to liquid 223 that hasbeen selectively deposited on substrate 201. In a preferred embodiment,substrate 201 is a carbon fiber layer.

Note: thermoplastic powder is used in some implementations of thisinvention. However, in some other implementations of this invention,thermoplastic powder is not used, and a liquid thermosetting polymer ora liquid thermoplastic is selectively applied to the substrate layers.

FIG. 3 is a cross-sectional view of three substrate layers 301, 302,303, after thermoplastic powder has melted, coated a portion of thesubstrate layers, cooled, and solidified, in an illustrative embodimentof this invention. A portion 305 of these substrate layers is coated bythe solidified thermoplastic. Another portion 307 of these substratelayers is not coated by the solidified thermoplastic. The details of thecoating may vary, depending on the implementation. For example, thesolidified thermoplastic may coat, infiltrate, penetrate, or encapsulatea portion of the substrate layer, or substructures in a portion of thesubstrate layer, such as, but not limited to, threads, short fibers,long fibers, whiskers, spherical particles, ellipsoidal particles,flakes, small platelets, small ribbons, and/or particulates of any othershape. The thickness of the coating may vary, depending on theimplementation. Likewise, the way in which the solidified thermoplasticconnects or bridges between substrate layers may vary, depending on theimplementation.

FIG. 4 is a cross-sectional view of the three substrate layers 301, 302,303 of FIG. 3, after excess substrate (element 307 in FIG. 3) has beenremoved. That is, FIG. 4 shows these three substrate layers, afterremoval of the portion 307 of the substrate that is not coated by thesolidified thermoplastic.

Rastering:

FIG. 5 shows apparatus used to selectively deposit liquid (to whichpowder adheres), in an illustrative implementation of this invention. Inthis implementation, registration guide posts 501 are inserted through asubstrate layer 503 in order to properly align the substrate layer 503.A solenoid valve 505 is used to selectively dispense liquid from aliquid reservoir 507 though a nozzle 509 unto the substrate layer 503.The nozzle 509 is rastered in a 2D plane 510 that is parallel to, andabove, the substrate layer 503, so that the liquid is selectivelydeposited at desired (x, y) coordinates of the substrate layer 503, andnot deposited in other areas of the substrate layer 503. To achieve thisrastering, a stepper motor 511 actuates two belts (not shown) thatcauses a support member (not shown) to move along two rails (not shown)in a direction parallel to the x axis. A second stepper motor (notshown) and third belt (not shown) are mounted on the support member, andare used to move a nozzle support (not shown) in a direction parallel tothe y axis. The nozzle 509 is attached to the nozzle support. Together,the two stepper motors can move the nozzle 509 to any desired (x, y)coordinate above the substrate layer. A microprocessor 513 controls thestepper motors and the solenoid valve, thereby controlling when andwhere liquid is dispensed on the substrate layer 503.

Alternatively, rather than rastering in a line-by-line pattern, thestepper motors may cause the nozzle 509 to move in other 2D patterns inthe 2D plane, in order to cause the liquid to be deposited at certain(x, y) coordinates.

FIG. 5 does not show apparatus for heating and pressing multiple layersof substrate, or for removing excess substrate. In some implementations,the substrate layer is moved to a different position before those stepsoccur.

Processors. In exemplary implementations, computer processors are usedto control the 3D printing process.

FIG. 6 is a block diagram that shows a plurality of processors, in anillustrative implementation of this invention. A CAD model of a desired3D object in STL file format is created using a remote processor 601.This processor 601 employs software (such as, for example, netfabb®Studio software) to create a machine-specific build file. Themachine-specific build file is exported to a second processor 603.Depending on the particular implementation, this second processor 603controls the operation, including movements, of 3D printer 610, whichmay include: (1) an inkjet head or other device that selectivelydeposits liquid, (2) actuators that spread out the powder on thesubstrate and then remove the excess powder, (3) a thermal print head,(4) a hot stamp press, and/or (5) actuators that feed or flip oversubstrate layers.

Alternatively, this invention may be implemented with other arrangementsof processors. For example, more than one remote processor and more thanone onboard processor may be employed, and any of the above tasks may behandled by one or more of these different processors.

Ink Jet Printer:

In some implementations of this invention, an ink jet printer is used toselectively deposit liquid on a substrate layer. The liquid isconventional ink used for an inkjet printer. Alternatively, water oranother wetting liquid may be used as the liquid. The ink jet head israstered (or otherwise moved in a 2D pattern) across the substratelayer, using x and y stepper motors. As the inkjet printer head israstered, it can print multiple lines of ink with each pass. After theliquid is selectively deposited on the substrate layer, the layer isflooded with powder (e.g., thermoplastic powder). The powder adhereswhere the liquid is present. Then excess powder (powder that does notadhere to the liquid) is removed. A heated press is used to melt thepowder and to press layers of substrate together. All of thesesteps—inkjet printing, application of powder, removal of excess powder,and the heated press or iron—may be automated, in order to improve theprecision and speed of steps in the process.

This approach (with an ink jet printer and heated press) has a number ofadvantages. First, it may be implemented using simple, low-costapparatus. Second, it is fast: for example, ink jet printers can achieverates of 30 sheets per minute. Third, objects can be printed in colorand decorated. For example, in a prototype of this invention, dyes orpigment-based inks can be used, allowing fully decorated parts to bemade. Fourth, the ink jet heads can be inexpensive. For example,disposable, inexpensive thermal inkjet heads (such as HP45 availablefrom Hewlett Packard Company) can be used.

This ink jet approach/embodiment may be scaled easily. For example, thethermoplastic may be selectively applied to large (long) sheets ofsubstrate. Unlike laser sintering and fused deposition, there is no needfor a precision oven. The surface tension and evaporation of the liquidcan be modified by using a liquid other than water, or by adding othercompounds (such as ethylene, propylene glycol or 2-pyrrolidinone) to thewater.

Prototypes:

The following is a description of three prototype implementations ofthis invention:

Prototype #1:

In a first prototype, the substrate is comprised of polyamide (nylon)fabric. A first layer of substrate is placed on a hot stamp press. Asecond layer of substrate is placed on another surface (not on the hotstamp press). Water is then selectively applied to that second substratelayer. The second layer is then flooded with Shaetti® SF 400thermoplastic powder. The powder adheres to the water that was appliedto the second layer. The second layer is turned upside down, whichcauses the excess powder (which is not adhering to the water) to falloff. The second layer of substrate is then placed in the hot stamppress, while still upside down, with the powder adhering to the bottomof the second layer. When it is so positioned, the second layer is ontop of the first layer. The hot stamp press then heats and presses thetwo layers together. The process is repeated by adding a third layer ofsubstrate, fourth layer and so on, each in the same manner as the secondlayer. Each time that the hot stamp press does a “stamp”, it melts thepowder beneath the top substrate layer. The resulting molten materialcoats a portion of the substrate layers, then cools and solidifies,causing the then current top and second-to-top layers of substrate toadhere to each other. The portion of the substrate to which the powderadhered is coated in a solidified plastic material.

After all of the layers of substrate have been added and pressedtogether, the resulting object is taken off the hot stamp press. It isthen placed in an aqueous solution of hydrochloric acid. Thehydrochloric acid causes the excess substrate, which is not coated bythe solidified material, to dissolve. In order to speed up thisdissolution, the solution may be heated and stirred by, for example, amagnetic stirrer. After the excess substrate is removed, what remains isthe desired 3D object. This 3D object comprises solidified plastic (thatresulted when the thermoplastic powder cooled) and the portion of thenylon substrate that it coats.

In this first prototype, each layer of substrate has guide holes in it.Registration guides (that are, for example, posts attached to the hotstamp press) are inserted into the guide holes of each layer ofsubstrate, in order to make the substrate layers align with each other.

In this first prototype, Scotchguard® Fabric & Upholstery Protector(available from 3M, St. Paul, Minn.) may be sprayed onto each substratelayer before liquid is selectively deposited on the layer. This reducesthe amount of liquid that is absorbed by the substrate and the distancethe liquid spreads in the substrate. Alternatively, or in addition, eachsubstrate layer may be suspended over a frame, so that the centerportion of the layer is not touching any solid surface. This, too, tendsto reduce the absorption of liquid by the substrate, and the spreadingof the liquid.

Alternatively, in this first prototype, an alcohol (instead of water)may be selectively applied to the substrate layers.

Alternatively, in this first prototype, the substrate layers may bealigned and placed, one on top of another, in a compressive device thatis tightened to apply pressure to compress the substrate layerstogether. This device, once tightened, may be placed in an oven (e.g., aconventional toaster oven).

In this first prototype, the excess substrate (comprised of polyamide)is removed with hydrochloric acid.

Prototype #2:

In a second prototype, water soluble paper is selectively printed withwater using a 0.005 inch minstac nozzle obtained from the Lee Company,Essex, Conn. (part INZA650935K). In this instance, the amount of waterdeposited at this step is not enough to substantially dissolve thepaper. The nozzle is rastered in a line-by-line pattern (or otherwisemoved in a 2D pattern) above the substrate layer using two steppermotors that move in x and y directions. A microcontroller controls thestepper motors. It also controls the opening and closing of the valve inthe nozzle. When the valve is open, water under pressure is deposited onthe substrate layer.

In this second prototype, the paper that is used has been cut on a lasercutter, with two registration holes in the top of the paper. Paper isinserted into a machine where it is aligned on a registration form, anda “slice” of the object is printed with water on the paper. The water isselectively printed in a pattern that corresponds to the particularslice. The paper is then flooded with Shaetti® SF 400 thermoplasticpowder which adheres only where the water has been deposited. The paperis then turned upside down and the excess powder falls off from theareas where no water has been deposited. The piece of paper for thefirst layer is then set on a registration form with two registrationrods, on top of a bottom sheet of paper that was previously placed inthe registration form. The paper with the powder attached is placedpowder side down. This paper is then tacked to the bottom sheet using atacking iron. This process is repeated multiple times until each layerof the object has been printed. The tacking iron is used to insure thatpowder remains attached to the paper after the water has dried.

In this second prototype, the sandwich of paper is clamped with aC-clamp using a rubber stopper between the C-clamp and the papersandwich so that the force is retained as the paper sandwich iscompressed when it is heated. This assembly is then put in an oven abovethe melting temperature of the thermoplastic powder and for a period oftime which is longer as the part becomes larger. This causes thethermoplastic powder to penetrate the paper and glue the sheets of papertogether. The paper stack is then removed from the oven and allowed tocool for about half an hour, allowing the thermoplastic to cool andsolidify. Then the stack of paper is placed in a stream of water from afaucet. The water may be hot, since elevated temperature helps indissolution. A jet of water (e.g., water pick) may also be used toaccelerate the removal of the excess paper (i.e., the paper that is notcoated with plastic). The excess paper is removed, resulting in a 3Dobject. Objects that are produced using this prototype are stiff andhave good mechanical integrity. Before the excess substrate is removed,it acts as support for the 3D object being produced, allowing for a widerange of geometries to be constructed.

In this second prototype, other methods for applying heat and pressuremay be used, instead of an oven and C-clamp. For, example, a heatedpress (such as a hot stamping press) can be used to apply heat andpressure to each substrate layer (or to a few substrate layers at atime). With a heated press, it can be easy to control the temperature,pressure and duration of each heat/pressure step. Or, for example, thepaper layers may be aligned and placed, one on top of another, in acompressive device that is tightened to apply pressure to compress thesubstrate layers together. The compressive device, once tightened, maybe placed in an oven (e.g., a conventional toaster oven). Thecompressive device may include springs or other elastic components thatcontinue to apply pressure even if the thickness of the paper layersdecreases (e.g., due to compression).

Prototype #3:

In a third prototype, an inkjet printer is used. The inkjet printerselectively deposits liquid on a substrate layer (so that the liquid ison some parts of the substrate layer and not on other parts of thesubstrate layer). In other words, the inkjet printer prints a pattern ofliquid on the substrate layer. The substrate layer is then flooded withthermoplastic powder. The powder adheres to the substrate in accordancewith the printed pattern (i.e., the powder adheres to the portion of thesubstrate layer where the liquid has been deposited, but does not adhereto the rest of the substrate layer).

Thus, an overall effect of the above steps in this third prototype isthat the thermoplastic powder is selectively deposited on the substratelayer in a pattern, where the pattern corresponds to the pattern ofliquid printed by an inkjet printer.

In this third prototype, a rectangular layer of substrate is taped to an8.5 inch by 11 inch sheet of conventional paper. When doing so, theouter edges of the substrate layer are aligned with a rectangle printedon the sheet of paper

Then, an HP 820CSE inkjet printer (manufactured by Hewlett PackardCompany, Palo Alto, Calif.) prints a pattern of ink on the substratelayer. Conventional ink for that printer is used. The printed patterncomprises a grid that defines a matrix of tiles. In this printedpattern, a different cross-sectional “slice” of a three-dimensionalobject is printed in each of the tiles, respectively.

In this third prototype, different types of substrate material (and,correspondingly, different ways to remove excess substrate) may beemployed. For example, the substrate may comprise PVOH. In that case,water may be used to dissolve the excess substrate. Or, for example, thesubstrate may comprise PLA. In that case, excess substrate may beremoved by placing the rectangular cuboid in a solution of methanol andKOH. In order to speed the removal, this solution may be agitated with amagnetic stirrer, or may be placed in an ultrasonic tank.

FIG. 7A shows a pattern that has been inkjet-printed on a substratelayer 701. The pattern comprises a grid 702 that defines a 4×3 matrix oftiles. Alternatively, the grid can be created by scoring or perforatingthe sheet to define the matrix of tiles. This can be accomplished usinga laser cutter, knife blade, die cutter or any other suitable tool ormethodology. Each tile is a pattern for a single “slice” of a desired 3Dobject. In the example of FIG. 7A, in each tile, respectively (e.g.,tile 703), a different cross-sectional “slice” (e.g., slice 704) of aring torus has been printed by the inkjet printer. In each tile (e.g.,tile 703), there is at least one “positive” area (e.g. slice 704),corresponding to the region of the slice that will be part of thedesired 3D object, and at last one “negative” area (e.g., area 710),corresponding to a region of the slice that will not be part of thedesired 3D object. The upper left tile 705 in FIG. 7A is a null slice ofthe ring torus, (i.e., it does not include a part of the ring torus).While the substrate layer shown in this example consists of 12 tiles,the number of tiles per substrate layer can be varied as desired andcould be more than 12 or as few as 2 per substrate layer.

FIG. 7A shows how the substrate layer is aligned with a sheet of paper707. On the sheet of paper 707, rectangles have been pre-printed.Substrate layer 701 is taped on paper 707 so that the outer edges ofsubstrate layer 701 align with one of these pre-printed rectangles onthe sheet of paper. More specifically, in FIG. 7A, three rectangles,nestled inside each other, have been pre-printed on the paper. The outerrectangle 711 and central rectangle 709 of these three rectangles arevisible in FIG. 7A. The innermost of these three pre-printed rectangleson sheet of paper 707 is not visible in FIG. 7A. However, the innermostrectangle is aligned with, and lies directly beneath, the outer edge 713of the rectangular grid (visible in FIG. 7A) that was printed onsubstrate layer 701 by the inkjet printer.

In the four corners of each tile, the pattern includes four registrationholes 723, 725, 727, 729, one hole per corner. Because the rim (which issquare in FIG. 7A) of each hole is stronger than the hole itself, thehole can simply be poked out by a hard instrument. Alternatively,registration holes may be cut out (e.g., by a laser cutter). In eithercase, once the holes are formed, registration pins may be insertedthrough the registration holes in order to align the “slices” or theobject.

In the example shown in FIG. 7A, a single sheet has a pattern for a 3×4array of slices (i.e., 12 slices per sheet). Slices from ten such sheetsmay be used to fabricate a 3D object comprising 120 slices.

Signatures (in the printing sense) may be used when grouping the slices.In the example shown in FIG. 7A, each signature might comprise 6 slices.A total of 20 signatures would then be used to fabricate a 3D objectcomprising 120 slices. For example, the slice in tile 710 is the firstslice out of 120 slices, and would be included in a first signature thatcomprises the first six slices out of the 120 slices.

After the inkjet printer prints the pattern on the substrate layer, thesubstrate layer is flooded with thermoplastic powder (e.g. Schaetti® Fix400 powder). The excess powder is then removed, by turning the paperupside down and tapping the paper with a finger. Other removal methodsmay be used, such as vacuuming or blowing the excess powder away.

The substrate layer is then aligned on a laser cutter. The laser cutterthen cuts lines that separate the substrate layer into the tiles andcuts two registration holes in each of the tiles

As an alternative to cutting a substrate layer to form individual tiles,the lines that define the grid can be scored or perforated using a lasercutter, knife, die cutter or other suitable tool or methodology. Thescoring or perforation can be done either after the powder is applied asdescribed above, or before the slices of the object are printed onto thetiles of the substrate layer. In this alternate embodiment, after thepowder is applied, some of the grid lines are cut so that the edges ofthe tiles that are defined by the grid line are separated, and then thetiles are folded to cause the tiles to be stacked one on top of theother in the correct order. A laser cutter, knife, due cutter, or othersuitable tool or methodology can be used to make these cuts.

FIG. 7B depicts a substrate layer in which the grid 740 has been definedby laser cutting perforations 742 at the grid lines. The slices of theobject have been printed onto the tiles and powder is applied in thesame method as described above. FIG. 7C shows the substrate of FIG. 7Bafter some of the grid lines have been cut. The cuts are made so thatthe tiles can be consecutively folded. In FIG. 7C, the cuts were madealong edges 744, 746, 748, 750, 752, 754.

The tiles are then folded to cause each tile to be stacked on top of orbelow a tile that shares a non-cut edge. Tile 705 is folded at edge 756so that tile 705 sits on top of tile 703. Stacked tiles 703, 705 arethen folded at edge 758 so that they sit under tile 760. Stacked tiles703, 705, 760 are then folded at edge 762 so that they sit on top oftile 764. This pattern of folding is continued until all of the tiles ona substrate layer are stacked. So, for the example of FIGS. 7B and 7C,stacked tiles 703, 705, 760, 764 are then folded at edge 766 so thatthey sit under tile 768. Stacked tiles 703, 705, 760, 764, 768 are nowfolded at edge 770 so that they sit on top of tile 772. Stacked tiles705, 703, 760, 764, 768, 772 are then folded at edge 774 so that theysit under tile 776. Stacked tiles 703, 705, 760, 764, 768, 772, 776 arethen folded at edge 778 so that they sit on top of tile 780. Stackedtiles 705, 703, 760, 764, 768, 772, 776, 780 are then folded at edge 782so that they sit under tile 784. Stacked tiles 703, 705, 760, 764, 768,772, 776, 780, 784 are then folded at edge 786 so that they sit on topof tile 790. Stacked tiles 703, 705, 760, 764, 768, 772, 776, 780, 784,790 are then folded at edge 792 so that they sit under tile 794.Finally, stacked tiles 703, 705, 760, 764, 768, 772, 776, 780, 784, 790,794 are then folded at edge 796 so that they sit on top of tile 798.

The finished stack 799 of tiles is shown in FIG. 7D. It will be clear toone of skill in the art of the invention that this exemplary foldingscheme can be generalized to grids of any number of tiles. The slices ofthe 3D object printed onto the tiles are arranged in sequence andoriented so that when the tiles are folded in this fashion, they arelocated in the right place and orientation in the stack of tiles. In oneembodiment, the software that creates the slides of the CAD model of theobject is used for this purpose. The software can include programming tocreate, arrange, and orient the slices automatically.

The folding of the tiles can be automated using mechanical apparatus, oralternatively, the tiles can also be folded manually. To aid an operatorto fold the tiles in the proper order, special marks may optionally beincluded on each tile. The marks can be geometric shapes or any othersuitable indicia. The marks can be added before the substrate layer isused for printing or they can be created by printing them onto the tilesat the same time that the slices are being printed. The marks arepositioned so that they will line up when the tiles are properlystacked. Thus, as each tile is folded upon another, the operator canvisually check to see if the marks are aligned. Additionally, oralternatively, numbers can optionally be included on each tile so thattiles that are adjacent when stacked bear consecutive numbers. Thenumbers can be added before the substrate layer is used for printing, orthey may be created by printing them onto the tiles at the same timethat the slices are being printed. In this way, an operator can visuallycheck to see if the tiles are in the proper order.

One benefit of folding the tiles is that it can be speedier than cuttingand stacking each tile individually. Another benefit is that it helps inaligning each tile on top of the other, so that the slices of the objectprinted on those tiles are properly aligned in terms of both orientationand precision. The physical connection between each layer to the layersabove and below it also helps to maintain the alignment between thelayers during the subsequent compression and heating steps.

In the example of FIGS. 7A-D, each substrate layer is divided into 12tiles, with a different “slice” of a ring torus being printed on eachtile, respectively. These tiles are then placed in a device for applyingpressure (a “compressive device”), one tile on top of another. Thecompressive device includes one or more elastic components (e.g.,springs) to maintain pressure on the substrate layers even if theycompress. The tiles are aligned by inserting two guide holes in eachtile through two guide posts in the press, respectively.

FIG. 8 shows a compressive device 803, after a number of substrate tiles(e.g., tile 801) have been placed in it, one on top of the other. Thesecan be tiles that have been individually placed one on top of another ortiles that have been stacked by folding tiles in the manner previouslydescribed. If more than 12 tiles are needed, then the process isrepeated, until enough all of the tiles required for fabricating theobject (all of the slices) have been produced.

In the example of FIGS. 7A-D, substrate tiles for all of the “slices” ofthe ring torus are placed into the compressive device. The total numberof substrate tiles required is more than 12. The process of printing 12slices on 12 tiles on a substrate layer is repeated, layer by layer,until tiles for all of the slices have been printed. Each of the tilesis cut or folded from a larger layer or sheet of substrate, and theindividual tiles themselves comprise the layers of the object beingfabricated. The substrate tiles (object layers) that have been insertedinto the compressive device are then compressed together by that device.

FIG. 9 shows substrate tiles (object layers) being compressed inexemplary compressive device 903. Screws 905, 907, 909, 911, plates 913,915, and spring 917 in the compressive device are used to exertpressure.

In this example, once tightened, the compressive device (with thesubstrate tiles in it) is then placed in a conventional toaster oven.The compressive device includes both a spring, to maintain pressure onthe substrate layers even if they compress, and a stand-off, clutch,brake, or damper to limit movement of the compressive device.Alternatively, the springs in the compressive device may be omitted andsimple mechanical pressure of the screws can be used. Alternatively, ahot stamping press can be used to apply pressure.

The heat from the oven causes the thermoplastic powder to melt. Themolten material coats the substrate layers. The compressive device (withthe object/substrate layers in it) is then removed from the oven, andthe object layers are allowed to cool. The molten material thensolidifies. As it does so, it binds (fuses) the substrate layerscomprising the object layers together.

FIG. 10 shows the substrate layers 1001, after they have been fusedtogether into rectangular cuboid 1003. In this example, a 3D toroid isbeing fabricated, with the upper-most slice 1009 of the toroid beingvisible at the top surface of the cuboid 1003. Two registration holes1007, 1009 are visible in excess substrate that will be subsequentlyremoved.

Excess substrate that has not been covered by the solidified material isthen removed. In the example shown in FIG. 11, a ring torus 1100 remainsafter the excess substrate in the rectangular cuboid 1003 of FIG. 10 hasbeen removed.

Many Ways of Implementing Invention:

This invention is not limited to melting of the powder, in which solidpowder becomes liquid. Other transitions may be employed. For example,the powder may undergo a glass transition that allows it to penetratethe substrate. Or, for example, the powder may be transformed into in abi-phasic material that can penetrate the substrate.

This invention is not limited to fibrous substrates. For example, thesubstrate may be a composite that comprises particles, ellipsoidalparticles, flakes, small platelets, small ribbons, or particulates ofany other shape, or a combination of two or more of these, which arebound or glued together by another material.

This invention may be implemented using grains of powder that eachencapsulate (or microencapsulate) a resin or other liquid. In theexample shown in FIG. 12A, a powder grain 1201 comprises a solid outerlayer 1205 of thermoplastic or thermoset plastic. The outer layer 1205encapsulates liquid 1203. The powder may be selectively deposited.Pressure (and heat) may be applied burst the encapsulation. The resin orliquid may then infiltrate into the substrate layers. The resin mayharden upon exposure to (1) air, (2) a reactant, reagent, catalyst orsolvent, or (3) electromagnetic radiation.

In an illustrative embodiment of this invention, grains of powderencapsulate (or microencapsulate) epoxy resin. Grains of epoxy hardenerare also mixed into the powder. The powder mixture is selectivelydeposited. Pressure (and heat) may be applied burst the encapsulation,so that the resin penetrates into the substrate layers and then hardens.In the example shown in FIG. 12B, the powder mixture comprises two typesof grains: completely solid grains of epoxy hardener 1207 and grainsthat comprise a solid outer layer 1205 that encapsulates a liquid epoxyresin 1203.

Alternatively, the substrate may be flooded with powder thatencapsulates liquid. Pressure may be selectively applied (e.g., with adot matrix print head) to burst the encapsulation, so that the liquidinfiltrates the substrate layers and then hardens.

In exemplary implementations of this invention, a variety of means maybe used to transform powder into a substance that flows and thensubsequently hardens. For example, the means may comprise a heatingelement. The heating element may comprise any artificial heat sourcethat heats by one or more of conduction, convection or radiation. Asnon-limiting examples, the heating element may comprise: (1) a resistoror any other resistive heating element; (2) any other device thatconverts electricity into heat by ohmic heating; (3) a hot stamp pressor any other apparatus for applying heat and pressure; (4) an oven; or(5) an artificial source of electromagnetic radiation, including a heatlamp, an artificial infrared light source, a laser; or an artificialsource of microwave radiation. Also, for example, the means may comprisean artificial pressure source, including a press, clamp, iron, roller,pump, piston, or elastic element (e.g. spring) for applying pressure.The pressure may be used, for example, to compress layers together or tosqueeze the flowing substance into interstices in the substrate layers.Or, for example, the pressure may be used to crush, rupture or burstgrains of powder that encapsulate liquid. The liquid may then flow, andmay harden or cause something else to harden. The heating element orpressure source may be configured to transform powder into a substancethat flows and then subsequently hardens. Also, for example, the meansmay comprise a reagent, reactant, catalyst, solvent or solute used in achemical reaction. The reaction may soften or harden all or a portion ofthe powder. An applicator may be configured to apply, deposit, ordeliver the reagent, reactant, catalyst, solvent, or solute to thepowder. Also, for example, the means may comprise an artificial sourceof electromagnetic radiation. The radiation may, for example, be usedfor hardening the powder, including by curing. The radiation source maybe configured to transform powder into a substance that flows and thensubsequently hardens

FIG. 13 is a high-level block diagram of some hardware that may be usedin this invention. One or more processors 1301 control an applicator1303, a heating element 1305, an actuator 1307, an artificial pressuresource 1309, and a stirrer in a container of liquid 1311. Applicator1303 deposits powder in positive regions, but not in negative regions,of substrate layers. Heating element 1305 transforms the powder intomatter that flows and then hardens. The resulting hardened material isdisposed in a spatial pattern that infiltrates the substrate layers.Artificial pressure source 1309 may comprise a press, clamp, spring,elastic element, or other device for compressing the substrate layers.The stirrer may be used to stir a liquid that is used for removingexcess substrate.

FIGS. 14A and 14B are each flow charts of steps used to fabricate a 3Dobject, in two different illustrative embodiments of this invention,respectively.

In the embodiment of FIG. 14A, the steps are: (a) positioning 1405powder on all or part of a substrate layer; (b) repeating 1410 step (a)for other substrate layers; (c) transforming 1415 at least some of thepowder into a substance that flows and subsequently hardens into ahardened material, which hardened material is disposed in a spatialpattern that infiltrates at least one positive region in a set of thesubstrate layers and does not infiltrate at least one negative region inthe set; and (d) removing 1420 material from at least one of thenegative regions in the set

In the embodiment of FIG. 14B, the steps are: (1) selectively depositing1430 powder on a positive region, but not on a negative region, of asubstrate layer; (2) repeating 1435 step (1) for other substrate layers;(3) transforming 1440 at least some of the powder into a substance thatflows and subsequently becomes the hardened material, which hardenedmaterial is disposed in a spatial pattern that at least partially fillsat least some interstices, which interstices are each, respectively,located inside at least one of the layers, respectively; and (4)removing 1445 material from at least one negative region of at least onesubstrate layer.

In some implementations of this invention, the melted or softened powdermay enter the substrate layers by absorption.

In another aspect, this invention may comprise an article ofmanufacture. Advantageously, in some implementations, using powderpermits the finished 3D product to have a high resolution in at leastone dimension. In one example: powder is selectively deposited onsubstrate layers. For each layer, two substeps occur: first, an inkjethead is used to dispense liquid, and second, powder is applied andadheres to the liquid. The powder is then heated and flows, infiltratingthe layers, and cooling into a solidified material that binds thesubstrate layers together. In this example, the spatial resolution of anexterior surface of the 3D product may be approximately equal to theresolution of the inkjet head in an x, y-direction and to the thicknessof a substrate layer in the z-direction.

In an illustrative implementation, an article of manufacture maycomprise substrate layers infiltrated by a hardened material. Thehardened material may be a thermoplastic. In one example, an exteriorsurface of the hardened thermoplastic may have a spatial resolution of60 or more dots per centimeter in at least one dimension, and thethermoplastic may have a viscosity of 50 or more centipoise at 50degrees centigrade above the thermoplastic's melting temperature. Or,for example, an exterior surface of the hardened thermoplastic may havea spatial resolution of 170 or less microns in at least one dimension,and the thermoplastic may have a melt flow rate of at least 70 grams/10minutes.

This invention may be implemented in many different ways. Here are someexamples:

This invention may be implemented as a method of fabricating a 3Dobject, which 3D object comprises a plurality of substrate layers thatare infiltrated by and bound together by a hardened material, the methodcomprising the following steps, in combination: (a) positioning powderon all or part of at least one of the layers; (b) repeating step (a) forremaining layers in the plurality of substrate layers; and (c)transforming at least some of the powder into a substance that flows andsubsequently hardens into the hardened material, which hardened materialis disposed in a spatial pattern that infiltrates at least one positiveregion in a set of the substrate layers and does not infiltrate at leastone negative region in the set; wherein the powder is transformed instep (c) after being positioned in either step (a) or step (b), andwherein the substrate layers have at least one material property that isdifferent than any material property of the hardened material.Furthermore: (1) the positioning may comprise selectively applying thepowder to part but not all of a surface of the layer; (2) thepositioning may be in accordance with a machine-readable digital modelof a slice of the 3D object; (3) the transforming may comprise meltingat least part of the powder; (4) the powder may comprise grains thateach, respectively encapsulate a liquid, and the transforming maycomprise rupturing, bursting or crushing at least some of the grains;and (5) the transforming may comprise a chemical reaction.

This invention may be implemented as a method of fabricating a 3Dobject, which 3D object comprises a plurality of layers and a hardenedsubstance that binds the layers together, the method comprising thefollowing steps, in combination: (a) selectively depositing powder on apositive region, but not on at least part of a negative region, of oneof the layers; (b) repeating step (a) for remaining layers in theplurality of layers; (c) transforming at least some of the powder intomatter that flows and subsequently becomes the hardened substance, whichhardened substance is disposed in a spatial pattern that infiltrates thelayers; and (d) removing material from at least one negative region ofat least one substrate layer; wherein the powder is transformed in step(c) after being deposited in either step (a) or step (b), and whereinthe substrate layers have at least one material property that isdifferent than any material property of the hardened substance.Furthermore: (1) the selectively depositing powder on a positive regionof the one of the layers may comprise a first substep and a secondsubstep, the first substep comprising selectively depositing liquid onthe positive region, and the second sub step comprising positioning thepowder on or adjacent to the one of the layers to adhere the powder tothe liquid; (3) the selectively depositing may further comprise a thirdsubstep, which third substep comprises removing powder that does notadhere to the liquid; and (4) the layers may comprise PET or PLA and analkali, alone or together with one or more other substances, may be usedfor the removing

This invention may be implemented as apparatus for fabricating a 3Dobject, which object comprises a plurality of layers and a hardenedsubstance, the apparatus comprising, in combination: (a) an applicator,the applicator being configured for selectively depositing powder in atleast some positive regions, but not in at least some negative regions,of at least some of the layers; and (b) a heating element, the heatingelement being configured for transforming the powder into matter thatflows and then hardens into the hardened substance, which hardenedsubstance binds the layers together and is disposed in a spatial patternthat infiltrates the layers; wherein the substrate layers have at leastone material property that is different than any material property ofthe hardened substance. Furthermore: (1) the apparatus may furthercomprise an artificial pressure source, the pressure source beingconfigured for applying pressure to one or more of the layers; (2) thepressure may be applied during softening of the powder; (3) theapparatus may further comprise one or more actuators, the one or moreactuators being configured for translating one or more of the powder andthe layers; (4) the apparatus may further comprise an additionalactuator, the additional actuator being configured for translating theapplicator into different positions while the applicator selectivelydeposits the powder; (5) the apparatus may further comprise a processor,the processor being configured for outputting control signals to controlthe applicator and heating element; (6) the processor may be adapted tooutput control signals to control the selectively depositing of powderfor each of the at least some substrate layers, respectively, inaccordance with digital data that specifies different slices,respectively, of the 3D object; and (7) the apparatus may furthercomprise a container, the container being configured for containing aliquid, which liquid includes a solvent or degrading material that isused for removing material from the at least some negative regions.

This invention may comprise apparatus for fabricating a 3D object, whichobject comprises a stack of substrate layers that have been infiltratedby a hardened material, the apparatus comprising, in combination: (a) anapplicator, the applicator being configured for positioning powder onthe layers; and (b) means for transforming the powder into a substancethat flows and then hardens into the hardened material, which hardenedmaterial binds the layers together and is disposed in a spatial patternthat infiltrates at least one positive region in a set of the layers anddoes not infiltrate at least one negative region in the set; wherein thesubstrate layers have at least one material property that is differentthan any material property of the hardened substance. Such apparatus mayadditionally include a mechanism for folding two or more tiles on asubstrate layer into a stack of substrate layer tiles.

This invention may comprise an article of manufacture comprising aplurality of layers that are infiltrated by and bound together by ahardened material, wherein the hardened material comprises either athermoplastic or thermosettable plastic and exhibits a set of one ormore characteristics, which set is sufficient for distinguishing thehardened material as having formed as a result of powder positioned onthe layers, respectively, at least partially softening and thenhardening. Furthermore: (1) the set of characteristics may comprise apattern resulting from at least some grains of powder not completelysoftening; (2) the set of characteristics may comprise a patternresulting from a first grain of powder flowing, after at least partiallysoftening, more viscously than another grain of powder flows, after atleast partially melting, or from part of the first grain flowing moreviscously, after at least partially softening, than another part of thefirst grain flows, after partially softening; (3) the set ofcharacteristics may comprise a crystalline or amorphous structureresulting from incomplete or nonhomogeneous melting of grains of powder;(4) the substrate layers may be woven; (5) the substrate layers may bewoven and fibrous; (7) the substrate layers may be non-woven; and (8)the article may include more than one hardened material, each of whichhas a different shade or color.

This invention may be implemented as an article of manufacturecomprising a stack of substrate layers that are infiltrated by ahardened material, wherein an exterior surface of the hardened materialhas a spatial resolution of 60 or more dots per centimeter in at leastone dimension, and wherein the hardened material comprises athermoplastic, which thermoplastic has an viscosity of 50 or morecentipoise at 50 degrees centigrade above the thermoplastic's meltingtemperature.

This invention may be implemented as an article of manufacturecomprising a plurality of substrate layers that are infiltrated by andbound together by a hardened material, wherein an exterior surface ofthe hardened material has a spatial resolution of 170 or less microns inat least one dimension, and wherein the hardened material comprises athermoplastic, which thermoplastic has a melt flow rate of at least 70grams/10 minutes.

This invention may be implemented as a process for fabricating a 3Dobject, which process comprises, in combination: (a) depositingthermosettable or thermoplastic powder on a second layer of substrate,in a pattern, for each substrate layer, respectively, defined by adigital description of a slice or section of a 3D object, (b)positioning the second layer of the substrate adjacent to a first layerof substrate so that edges of the first and second substrate layers arealigned and so that powder that was deposited on the second layer isbetween the first and second layers, (c) repeating step a with respectto a third layer of substrate, (d) positioning the third layer substrateadjacent to the second layer so that edges of the second and thirdlayers are aligned and so that powder that was deposited on the thirdlayer is between the second and third layers, (e) repeating steps (c)and (d), layer by layer, until powder has been selectively deposited onsubstrate layers corresponding to all of the layers of the 3D object,(f) applying sufficient heat and pressure to at least two of thesesubstrate layers to (1) cause at least a portion of the deposited powderto melt or soften, and (2) cause that melted or softened powder to coatat least a portion of the substrate layers, (g) allowing the melted orsoftened powder to cool, so that, upon cooling, the resultingthermoplastic or thermoset material binds together at least twosubstrate layers, which two layers are adjacent to each other, and (h)removing a portion of the substrate layers, which portion is not coatedby the resulting thermoplastic or thermoset material. Depending on theparticular implementation of this process, each of steps (f), (g) and(h) may occur either once, or more than once, during the process. Forexample, steps (f), (g) and (h) may occur once per layer, or once everyfive layers.

This invention may be implemented as a process for fabricating a 3Dobject, which process comprises, in combination: (a) depositingthermosettable or thermoplastic powder on two or more tiles defined on alayer of substrate, in a pattern, for each tile of the substrate layer,respectively, defined by a digital description of a slice or section ofa 3D object, (b) folding the tiles of the substrate along a common edgebetween each two adjacent tiles on the substrate so that powder that wasdeposited on a tile is aligned with powder that was deposited on atleast one adjacent tile, (c) repeating steps a and b with respect to asecond or more layers of substrate if needed, (d) adding the stack orstacks of tiles formed in step c to the stack of tiles formed in step b,(e) applying sufficient heat and pressure to the stack of substratelayers to (1) cause at least a portion of the deposited powder to meltor soften, and (2) cause that melted or softened powder to coat at leasta portion of the substrate layers, (f) allowing the melted or softenedpowder to cool, so that, upon cooling, the resulting thermoplastic orthermoset material binds together at least two substrate layers, whichtwo layers are adjacent to each other, and (g) removing a portion of thesubstrate layers, which portion is not coated by the resultingthermoplastic or thermoset material. Depending on the particularimplementation of this process, each of steps (e), (f) and (g) may occureither once, or more than once, during the process. For example, steps(e), (f) and (g) may occur once per stacked tiles of a single substratelayer, or once every two or more stacks of tiles from substrate layers.

This invention may also be implemented as a process for fabricating a 3Dobject, which process comprises, in combination: (a) depositingthermosettable or thermoplastic powder on two or more tiles defined on alength of substrate, in a pattern, for each tile of the substrate layer,respectively, defined by a digital description of a slice or section ofa 3D object, (b) folding the tiles of the substrate along a common edgebetween each two adjacent tiles on the substrate so that powder that wasdeposited on a tile is aligned with powder that was deposited on atleast one adjacent tile, (c) applying sufficient heat and pressure tothe stack of substrate layers to (1) cause at least a portion of thedeposited powder to melt or soften, and (2) cause that melted orsoftened powder to coat at least a portion of the substrate layers, (d)allowing the melted or softened powder to cool, so that, upon cooling,the resulting thermoplastic or thermoset material binds together atleast two substrate layers, which two layers are adjacent to each other,and (e) removing a portion of the substrate layers, which portion is notcoated by the resulting thermoplastic or thermoset material. Dependingon the particular implementation of this process, each of steps (c), (d)and (h) may occur either once, or more than once, during the process.For example, steps (c), (d) and (e) may occur once per every two stackedtiles, or once every three or more stacked tiles from the length ofsubstrate.

This invention may also be implemented as a process for fabricating a 3Dobject, which process comprises, in combination: (a) depositingthermosettable or thermoplastic powder on two or more tiles defined on alength of substrate, in a pattern, for each tile of the substrate layer,respectively, defined by a digital description of a slice or section ofa 3D object, (b) rolling up the two or more tiles as and until all ofthe tiles for fabricating the 3D object are powdered per step (a); (c)unrolling the two or more tiles and folding the tiles of the substratealong a common edge between each two adjacent tiles on the substrate sothat powder that was deposited on a tile is aligned with powder that wasdeposited on at least one adjacent tile, (d) applying sufficient heatand pressure to the stack of substrate layers to (1) cause at least aportion of the deposited powder to melt or soften, and (2) cause thatmelted or softened powder to coat at least a portion of the substratelayers, (e) allowing the melted or softened powder to cool, so that,upon cooling, the resulting thermoplastic or thermoset material bindstogether at least two substrate layers, which two layers are adjacent toeach other, and (f) removing a portion of the substrate layers, whichportion is not coated by the resulting thermoplastic or thermosetmaterial. Depending on the particular implementation of this process,each of steps (c), (d), (e) and (f) may occur either once, or more thanonce, during the process. For example, steps (c), (d), (e) and (f) mayoccur once per every two stacked tiles, or once every three or morestacked tiles from the length of substrate.

This invention may also be implemented as a product produced by any ofthe processes described in the preceding paragraphs.

This invention may be implemented as an article of manufacture,comprising at least twenty layers of substrate, each layer being boundto at least one adjacent layer by (and at least partially coated by) amaterial that comprises a thermoplastic or thermosettable polymer.Furthermore, depending on the particular embodiment of this article ofmanufacture: (1) the substrate layer may be woven, (2) the substratelayer may be woven and fibrous, (3) the substrate layer may benon-woven, (4) the substrate layer may be non-fibrous, (5) at least aportion of the external, macroscopic geometry of the substrate may bepolyhedral in shape, (6) the macroscopic exterior of the article ofmanufacture may include multiple rectilinear faces in different planes,(7) the macroscopic exterior of the article of manufacture may definemultiple compound or complex curves, (8) substrate layers of sucharticle may be coated at least in part with a repellant or sizing, (9)different portions of the polymer may have different colors, and (10)the polymer may cover fibers in substrate layers. Each layer can beplanar or flat.

This invention may be implemented as apparatus comprising, incombination: (a) at least one applicator for depositing thermoplastic orthermosettable powder on multiple layers of substrate, in a pattern, foreach substrate layer, respectively, defined by a digital description ofa slice or section of a 3D object, (b) at least one heat source forapplying heat to the substrate layers, (c) at least one pressure sourcefor applying pressure to the substrate layers, and (d) one or morecomputer processors for (I) accepting and processing digital datadescribing a section or slice of a 3d object, and (II) outputtingcontrol signals for controlling the operation of the applicators. Theapparatus may further comprise one or more of the following: (1) acontainer for containing a liquid, which liquid includes a solvent ordegrading material that is used for removing excess substrate, theexcess substrate being that portion of the substrate that is not coatedby thermoplastic or thermoset material after it melts or softens andthen cools , (2) a heat source for heating the liquid solvent ordegrading material, and (3) one or more actuators for translating one ormore of the powder, substrate sheets and the finished or partiallyfinished 3D object. Also, depending on the particular embodiment of thisarticle of manufacture, the one or more computer processors may do oneor more of the following: (1) accept and process data from one or moresensors, such as heat or pressure sensors, or sensors for determiningwhether and to what extent adjacent substrate layers are aligned, (2)control the at least one heat source, (3) control the at least onepressure source, (4) control the one or more actuators, and (5) acceptdata indicative of input from a human user.

In another aspect, this invention comprises a 3D object fabricated usingany of the fabrication techniques described above. For example, such a3D object may be comprised of composite materials. These compositematerials may comprise substrate layers coated by solidifiedthermoplastic or thermoset polymer.

FIG. 15 shows part of an abrasive blasting apparatus 1501, as it startsto abrade the excess region from a stack 1503 of carbon fiber layers. InFIG. 15, the abrasive blasting has not yet removed any of the excessregion. The stack 1503 of layers had been fused together whenthermosetting or thermoplastic powder hardened.

FIG. 16 is a photograph of a 3D object, comprising a carbon fibercomposite material, which was fabricated by a prototype of thisinvention. FIG. 16 is a photograph of a vase, after excess regions inthe stack of carbon fiber layers have been removed by abrasion. Theremaining portion of the stack corresponds to the vase shape of thetarget 3D object. The excess regions that were removed were weaker (morefragile or friable) and were easier to abrade than the printed portion,because no thermosetting resin or thermoplastic powder hardened on theexcess regions.

In exemplary implementations of this invention, multiple “slices” of adesired 3D object may be printed on a single sheet. Slices from multiplesheets may be used to fabricate the desired 3D object. The slices may becut from the sheet and stacked individually, or folded into a stack.Alternatively, multiple “slices” of a desired 3D object may be printedon a single length of substrate material. The slices may be cut from thesheet and stacked individually, or folded into a stack.

In an alternative embodiment to that depicted in FIGS. 7B-D, a roll 1710of substrate material can be perforated 1720 along its width atintervals of equal length, as shown in FIG. 17A. The portion 1730, 1732,1734 of the roll between each two perforations 1720 defines a tile onwhich a slice 1740, 1742, 1744 of the object is printed. After thepowder has been applied to a tile in the manner described above, thetile 1732 can be folded onto the previously powdered tile 1730 in anaccordion or fan-like fashion, as shown in FIG. 17B. Alternatively, theprinted and powered tiles can be rolled up until all of the tiles on theroll have been printed and powdered. Then, after all of the tiles forthe part are completed, they can be unrolled and fan-folded. In thisperforated roll embodiment, the slices of the 3D object printed onto thetiles are again arranged in sequence and oriented so that, when thetiles are folded, they are located in the right place and orientation inthe stack of tiles.

Illustrative Implementation Using Thermoplastic Polymer Powder

In an illustrative implementation of this invention, a composite 3Dobject is produced as follows:

-   1. Cut nonwoven carbon fiber substrate layer on laser cutter. Cut    registration holes into the layer. The substrate can be cut in    advance of the rest of the process.-   2. Put nonwoven substrate layer on registration post of printer.-   3. “Print” a slice. (In this step, liquid is selectively applied to    the carbon fiber substrate layer, e.g., by inkjet printing).-   4. Remove carbon fiber substrate layer from printer.-   5. Flood carbon fiber substrate layer with thermoplastic powder. The    powder adheres or “sticks” to the substrate only where the liquid    was applied.-   6. Remove excess powder by turning carbon fiber substrate layer over    and shaking until excess powder it falls off.-   7. Remove any remaining excess powder with a stream of compressed    air.-   8. Place carbon fiber substrate on a heated surface (e.g., a hot    griddle or other heating element) and melt the powder that adhered    to the printing liquid. Preferably, the heated surface has been    previously treated with polytetrafluoroethylene, so that the carbon    fiber substrate does not stick to the heated surface. Alternatively,    a layer of another material may be interposed between the heated    surface and the carbon fiber substrate, to prevent sticking-   9. Place the printed carbon fiber substrate on a fixture using    registration holes to align.-   10. Return to step 2 until all layers have been printed and placed    on the fixture, creating a stack of printed carbon fiber/polymer    powder layers-   11. Place the stack into a compression device. Then use the    compression device to apply pressure to the stack. The compression    device may include, for example (1) springs for applying    compression; and (2) bolts or standoffs for limiting the amount that    the substrate layers are compressed.-   12. Preheat oven.-   13. Put compression device (with stack of carbon fiber layers in it)    in oven.-   14. Heat the compression device (with the carbon fiber layers in it)    for appropriate time.-   15. Remove compression device from oven.-   16. Let compression device cool to room temperature.-   17. Open up the compression device (e.g., in some cases, by    unscrewing nuts).-   18. Remove fused 3D object from the compression device.-   19. Remove the excess region of each substrate layer by abrasive    blasting. The excess region is the portion of the substrate layer    that was not covered or permeated by the melted thermoplastic    material.

In exemplary implementations of this invention, a composite 3D object isproduced, layer by layer, using carbon fiber substrate layers. A CADmodel of the desired 3D object is produced first. Then a softwareprogram (e.g., a Netfabb® program) slices the CAD model into slices ofcorrect thickness, and produces bitmaps for each layer.

A non-woven carbon fiber substrate may be used. Alternatively, woven orchopped carbon fiber substrate may be used.

An applicator may selectively deposit liquid on each carbon fibersubstrate layer, respectively. In some implementations of thisinvention, the applicator may comprise, for example, an inkjet head. Theinkjet head may be housed in an inkjet printer. Alternatively, theinkjet head may be affixed to another device that is configured toposition the inkjet head for printing, e.g., by rastering or moving theinkjet head to a particular (x,y) position over the carbon fiber layer.The inkjet head may be a thermal head or, alternatively, any other typeof inkjet head, including a piezoelectric head.

The applicator may move over the carbon fiber substrate layer. As itdoes so, the applicator may “print” a swath of the bitmap onto thecarbon fiber by selectively depositing liquid onto the carbon fiber. Awide variety of fluids may be deposited by the applicator. For example,conventional inkjet ink may be used. Alternatively, the fluid in theapplicator may be a mixture of distilled water and 2-Pyrrolidone. Forexample, the mixture may comprise 10% to 50% 2-Pyrrolidone, and the restdistilled water. The mixture (of distilled water and 2-Pyrrolidone) maybe used for the purpose of reducing the evaporation rate of the fluidfrom the carbon fiber. Other fluids (e.g., glycols) can be used for thispurpose.

In a prototype of this invention, the applicator comprises an HP45Ainkjet cartridge (available from Hewlett-Packard Company).

The carbon fiber layer may then be removed from the apparatus where theliquid was dispensed. The carbon fiber layer may then promptly, so thatthe liquid does not evaporate, be flooded with nylon powder. Forexample, the nylon powder may have an average grain size in the range of50 to 100 microns. Alternatively, other polymer powders such aspolyethylene or PEEK (polyether ether ketone) can be used.Advantageously, PEEK is a high performance resin.

Powder adheres where the liquid was deposited by the inkjet head. Theexcess powder (which did not adhere to the deposited liquid) can beremoved by shaking the substrate layer upside down and then blowing itwith an air hose. This removes the excess powder that may have beentrapped in the crevices of the substrate layer. The carbon fiber layermay be placed on a heated surface (e.g., a griddle) or placed adjacentto any heating element. The heat melts and thus better attaches theremaining polymer powder so that the remaining powder tends not to bedisplaced in further handling.

Each of the sheets of carbon fiber, or multiple tiles on each sheet ofcarbon fiber that are folded into a stack, or multiple tiles on a lengthof carbon fiber folded into a stack, may then be placed on fourregistration posts in a compressive device. The process above (print onsubstrate layer, then put substrate layer on the registration posts) maybe repeated until all of the carbon fiber layers have been “printed”with thermoplastic powder and placed on the registration posts of thecompressive device. The compressive device may include one or moreplates, springs, nuts and bolts to apply pressure to the stack of carbonfiber layers. The pressure may compress the stack. The compressivedevice may be configured to apply a constant amount of pressure even asthe dimensions of the stack change under heat and pressure. A standoff,separator or other mechanical component (e.g., a nut) can be used tomaintain a minimum distance past which the stack of carbon fiber layerscannot be compressed.

The compressive device is placed in an oven. The time spent in the ovenand the temperature of the oven may be chosen depending on the size ofthe desired object. The heating causes the layers to fuse together. Asthe powder melts, it covers the fibers. The compressive device is latercooled and the molten material hardens. After that, bolts holding theplates are loosened and the stack of layers is removed from thecompressive device.

Abrasion may be used to remove excess regions of carbon fiber layers(where the melted powder did not coat or infiltrate). Carbon fiber isquite fragile in bending and can be abraded. However, the portion of thesubstrate layer which has been impregnated with the thermoplastic orthermoset material is quite hard and stiff and resistant to abrasion.The largest portion of the excess region may be removed by scraping witha dental tool. Also, for many geometries, the final removal can be donewith a wire brush. In addition, abrasive blasting can be used to removethe uncoated carbon fiber. Additionally, abrasive blasting can clearinternal channels in the 3D object.

After removing the excess region, the result is a stiff 3D printedcarbon fiber composite of nearly arbitrary geometry. This fibercomposite is fabricated without the use of tooling and in accordancewith a CAD model.

If woven fabric is used, then the orientation of the carbon fiber fabriccan be adjusted and the weave of the fabric changed so that layers mayhave different orientations to give the part greater strength in variousdirections.

In exemplary implementations of this invention, no mold design isrequired. Thus, each part can be different and customized. So forexample door panels of cars can be made which are customized by and forthe customer. In contrast, in conventional car manufacturing: car panelsare stamped out of metal; tooling costs can be extremely high; the costsof the presses can be large; and the time to produce the tooling can belong. In exemplary implementations, the present invention can overcomeall of these problems.

In some implementations, a composite material including carbon fiber isproduced. The composite material may exhibit desirable electricalcharacteristics. For example, if the carbon fibers in the composite arecontinuous, the composite may exhibit appreciable electricalconductivity.

Ferrite particles or other materials can be included with the resin orpowder to reduce the radar signature of the part for use in stealthaircraft and other radar avoiding devices.

Alternatively, other types of substrates may be used, including otherfabrics that have similar properties. For example, other substratematerials that can be abraded or abrasively blasted (such as fiberglass,ceramics, or polymers such as certain polyesters) may be used.

In some implementations of this invention, all of the steps areautomated.

In some implementations of this invention, multiple “slices” are“printed” on each substrate layer. For example, for a 3D object thatcomprises 144 slices, 12 substrate layers may be used, and 12 slices maybe printed per substrate layer. In this case, particularly if the entireprocess is automated, it may be preferable to print, on the first sheet,slices 1, 13, 25, . . . 133, on the next sheet, slices 2, 14, 26, . . .134, and so on. That way, for example, the upper right slice on sheets 1to 12 may comprise a signature of slices 1 to 12; an upper middle sliceon sheets 1 to 12 may comprise a signature of slices 13 to 24, and soon. In this example, the 144 slices may be cut and stacked initiallyinto 12 signatures, and the 12 signatures may then be stacked togetherin order (e.g., on registration posts in a compressive device).

In some implementations of this invention, no powder is used. Athermosetting liquid or a thermoplastic liquid may be selectivelyapplied to a carbon fiber substrate. The liquid penetrates or coats aregion of the carbon fiber substrate. When the liquid later cures orhardens in that region, it produces an extremely stiff carbon fibercomposite material. This also acts to bond the layers together andpressure may be used to create a better bond and also to compress thesubstrate. In a region of the substrate where no liquid is applied (anexcess region), the carbon fiber remains friable. The excess region isremoved by abrasive blasting.

In implementations in which no powder is used, the liquid that isapplied may comprise for example: uncured epoxy resin, uncured acrylicresin, or UV curable resin. For example, low melting point, lowviscosity polyethylene may be used with inkjet heads.

In some implementations, cut up carbon fiber is used. The cut up carbonfiber may be saturated, coated or infiltrated by a liquid thermosettingpolymer or liquid thermoplastic. For example, the liquid may comprise anepoxy resin or acrylic resin. In either case, the resin (or otherliquid) can penetrate or coat the cut up carbon fiber fabric, and thencure.

Alternatively, in some implementations, different materials may be usedin different layers. For example, in an illustrative implementation,some of the layers may comprise carbon fiber and other layers maycomprise other materials, such as polyester. Or, for example, fibers maybe oriented in different directions in different layers. Or, forexample, different thermosetting or thermoplastic material may beselectively applied, in different substrate layers.

A wide variety of registration/alignment techniques may be used in thisinvention.

For example, registration holes and posts may be employed forregistration. For example, each carbon fiber substrate layer may be cutso that it has four registration holes, one hole on each corner. Thiscan be done with a laser cutter. Or, for example, a rim for eachregistration hole may be printed, and then a hole in the middle of therim may be poked out or otherwise removed.

After being printed, the carbon fiber substrate layer may be placed on aset of four registration pins (so that the four registration pinspenetrate the four registration holes).

In another example, tiles defined on a substrate layer can be foldedinto a stack of layers, or tiles defined on a length of substrate can befolded into a stack of layers. This can be done alone, or in combinationwith the use of registration holes and posts, or with any of the manyother alignment mechanisms known in the art of the invention.

Or, for example, self-alignment may be employed. If an applicator (e.g.,inkjet printer) is configured to always print within the exact sameregion, this fact can be exploited to achieve self-alignment. Forexample, a bottom substrate layer may be held firmly in place on aflatbed printer. Thermoplastic or thermosetting polymer may beselectively applied to the layer by an applicator (e.g., an inkjetcartridge). Another substrate layer may be added. Then the thermoplasticor thermosetting polymer (which was applied to the bottom layer) may beheated and then cooled (or pressed or mixed with a curing agent or otherotherwise cured). A hardened or cured material then results, which fusesthe first and second layers. This process may be repeated, layer bylayer. In this example, the substrate layers are self-aligned, because(i) the printer always prints within the exact same region, and (ii) thebottom layer is held firmly in place.

The order in which steps occur may vary. For example, heat or pressureor both may be applied once for each layer, for at least most of thelayers. Or, for example, heat or pressure or both may be applied lessfrequently, such as (1) only once every t layers, where t is an integergreater than one, or (2) only once at all, after the thermosetting orthermoplastic material is selectively applied to each of the substratelayers and all of the substrate layers have been positioned in a stack.

Or, for example, liquid may be selectively applied for just one “slice”of the 3D object, then that “slice” may be flooded with powder, then theexcess powder for that slice may be removed, and then the process may berepeated for the next step, and so on, layer by layer.

Or, for example, liquid may be selectively applied to print a group of“slices” on a single sheet of the 3D object. Then the whole group ofslices on that single sheet may be flooded with powder, then the excesspowder for that group of slices may be removed, and then the process maybe repeated for the next group of slices, and so on, group by group.

In some implementations of this invention, a powder may comprise amixture that includes microencapsulated thermosetting resin and a powderbased hardener. As discussed above, the powder mixture may beselectively applied (including by first selectively applying fluid to asubstrate, and then flooding the substrate with powder so that powderadheres to the liquid, and then removing the excess loose powder). Thepowder mixture may then be crushed, so that the microcapsules burst orleak, the thermosetting polymer and curing agent mix, and thethermosetting polymer is cured. The cured material may infiltrate orcoat a portion of each substrate layer, respectively, and the excessportion of each substrate layer may be removed, e.g. by abrasiveblasting.

This invention may also be implemented as a 3D composite objectfabricated by a 3D printer. Such a 3D object may comprise layers ofcarbon fiber substrate that were fused together by thermoplastic or athermoset. In some cases, the hardened material in the 3D object mayhave characteristics indicative of the fact that the thermoplasticplastic was in powder form immediately before melting, including partialmelting. In some cases, the hardened material in the 3D object may havecharacteristics indicative of the fact that pressure was applied toburst a powder mixture that includes microencapsulated thermosettingpolymer and power based hardener. In some cases, the carbon fiber may bearranged in the 3D object in a pattern indicative of the fact that,before the thermoset or thermoplastic hardened, the carbon fibers werecut up, were loose, or otherwise did not comprise entire, integralsheets of carbon fiber. In some cases, some substrate layers in the 3Dobject may comprise carbon fiber and other substrate layers in the 3Dobject may comprise another material. In some cases, the orientation orweave characteristics of the carbon fiber substrate in the 3D object mayvary from layer to layer. In some cases, the hardened thermoplastic orthermoset material may contain chemicals or other characteristicsindicative of the fact that the material, before it hardened, wasejected by an inkjet cartridge or inkjet head, or by some otherparticular type of applicator.

According to principles of this invention, abrasive blasting may be usedto remove material in a wide range of 3D printing technologies,including fused deposition. Abrasive blasting has the advantage of beingfaster than many other subtractive techniques.

In exemplary implementations, the hardware of this invention may includeany one or more of the following components, together or in combination:(1) applicators, including applicators for selectively applying liquidto substrate layers, (2) positioning apparatus, including positioningapparatus for rastering or otherwise moving an applicator whenselectively depositing liquid or powder, (3) vessels, containers, bins,pipes, hoses or other channels for storing or moving materials used infabricating a 3D object, including vessels, containers, bins, pipes,hoses or other channels for storing or moving any thermoplastic,thermosetting polymer, curing agent, or other raw or intermediatematerial used in fabrication, and including vessels, containers, bins,pipes, hoses or other channels for storing or moving any fluids,including compressed gas, used in abrasive blasting or any othermanufacturing step, (4) substrate manipulators, including substratemanipulators for shaking, rotating, translating, vibrating or vacuumingsubstrate layers, (5) heating or compressive apparatus, includingheating or compressive apparatus for heating or compressing stacks ofone or more substrate layers, and including heating elements, (6)subtractive manufacturing apparatus, including abrasive blastingapparatus, bristle blasting apparatus, abrasion apparatus, rotarybrushes, wire brushes, sandpaper, emery paper, belts, sanders, files,saws, drills, burrs, awls, scrapers, scalers, or curettes, and furtherincluding any of the foregoing configured for removing excess regions ofsubstrate or removing raw materials or intermediate materials employedin fabrication, including abrasive blasting apparatus for abradingexcess regions of substrate layers, (7) actuators (including motors,engines transmissions, power trains, pumps, fans or robotics) foractuating motion of any the hardware described above or for actuatingmotion of any material (including powder, or any material in any phase,including solid, liquid, gas) used in fabricating a 3D object, (8)additive manufacturing apparatus of any kind, (9) electronic devices,including electronic memory devices, and (10) processors, includingprocessors for generating CAD models of target 3D objects, producingslices and bitmaps, outputting control signals to control the otherhardware described above, receiving signals indicative of human input,outputting signals for controlling output of information in humanperceivable form, and reading data from, and writing data to, one ormore electronic memory devices. Just to be clear, the components in thepreceding sentence are neither human nor part of a human body.

Alternatively, in some implementations of this invention in which powderis employed, the powder may be deposited using a selective depositiontechnique similar to that employed in xerographic printing. In thisapproach, an electrical charge is imparted to powder particles, whichare directed toward the substrate layer, and then selectively adhere tosome portions of the substrate but not others, due to electrostaticattraction or repulsion. The powder particles adhere to portions of thesubstrate that have an opposite electrical charge (or that are adjacentto a surface that has such a charge), and are repelled from portions ofthe substrate that have the same electrical charge (or that are adjacentto a surface that has such a charge).

Alternatively, in some implementations of this invention in which powderis employed, the powder may be deposited using a selective depositiontechnique similar to that employed in magnetographic printing. In thisapproach, powder selectively adheres to some portions of the substratelayer, but not others, due to magnetostatic interactions between thepowder and the substrate layer (or a surface adjacent to the substratelayer). For example, the powder may be a single component magnetictoner, or may comprise a colloidal suspension (e.g., a ferrofluid) ormay be a dual component toner. A variety of magnetic pigments, such asmagnetite (Fe₃O₄) or ferric oxide ((Fe₂O₃), may be used for the toner inthis approach.

As used herein, the following terms expressly mean:

The terms “a” and “an”, when modifying a noun, do not imply that onlyone of the noun exists.

An “applicator” means a device for applying a substance to a surface, orotherwise depositing, dispensing or moving the substance. For example,the substance may be a powder or a liquid. For example, an applicatormay comprise an inkjet head.

The word “coat” means to (at least partially) coat, infiltrate,penetrate or encapsulate. Grammatical variations of “coat” shall beconstrued accordingly. To coat a substrate means to coat the substrateor substructures of the substrate (such as threads, short fibers, longfibers, whiskers, spherical particles, ellipsoidal particles, flakes,small platelets, small ribbons, particulates of any other shape).

The term “comprise” means include without limitation. If A “comprises” Xand Y, this does not mean that A consists solely of X and Y. Instead, itmeans that A consists of at least X and Y.

The phrase “harden into” does not imply or exclude any displacement,translation or other movement.

A “heating element” means an artificial heat source that heats by one ormore of conduction, convection, radiation or induction. A “heatingelement” includes, among other things: (1) a resistor or any otherresistive heating element; (2) any other device that convertselectricity into heat by ohmic heating; (3) a hot stamp press or anyother apparatus for applying heat and pressure; (4) an oven; (5) aninductive heater; and (6) an artificial source of electromagneticradiation, including a heat lamp, an artificial infrared light source, alaser, or an artificial source of microwave radiation.

The fact that an “example” or multiple examples of something are givendoes not imply that they are the only instances of that thing. Anexample (or a group of examples) is merely a non-exhaustive andnon-limiting illustration.

The terms “include”, “includes”, “including” shall be construed broadly,as if followed by the words “without limitation”.

To “infiltrate” a layer includes (a) to infiltrate or penetrate into theinterior of the layer and to at least partially cover at least someinterior substructures of the layer (or of the region); (b) to beabsorbed into the layer, or (c) to be arranged in a pattern that resultsfrom infiltrating as described in (a) or (b). For example, a spatialpattern “infiltrates” a layer if the pattern results from infiltratingas described in (a) or (b). Also, for example, a hardened material“infiltrates” a layer if the hardened material is arranged in a patternthat results from infiltrating as described in (a) or (b). To infiltratea region of a layer shall be construed in like manner as to infiltrate alayer. Unless the context requires otherwise, if a substance x“infiltrates” substance y, this implies that x has at least one materialproperty that is different than any material property of y.

To “melt” includes (1) to melt or soften by the application of heat and(2) to dissolve.

A “negative” region of a substrate layer, which layer is used infabricating a 3D object, means a region that is not (or will not be)included in the 3D object when fabrication of the 3D object is complete.

The term “or” is an inclusive disjunctive. For example “A or B” is trueif A is true, or B is true, or both A or B are true.

A “positive” region of a substrate layer, which layer is used infabricating a 3D object, means a region that is (or will be) included inthe 3D object when fabrication of the 3D object is complete.

The term “powder” includes (1) a material comprising entirely solidgrains, (2) a material comprising at least some grains that each,respectively, encapsulate a liquid, (3) any granular material, and (4) amaterial comprising solid particles that may flow, relative to eachother, when accelerated.

A “set” consists of one or more elements. The term “set” does notinclude an empty set with no elements.

To “soften” includes (1) to soften below a melting temperature and abovea glass transition temperature, (2) to melt above a melting temperature,(3) to transition from a higher to a lower elastic modulus, (4) totransition from a higher to a lower viscosity, or (5) to otherwisesoften. The adjective “soft” shall also be construed in like manner. Forexample, the adjectives “soft” and “softened” each include “melted”.

A list of multiple steps in a process does not imply, except to theextent that the context requires otherwise, that: (1) the steps occur inany particular order or sequence, including the order or sequencelisted; (2) the steps occur only once; (3) the different steps occur thesame number of times during the process, or (4) a particular step isapplied to the same thing each time that the particular step occurs (forexample, except to the extent that the context requires otherwise, aspecific step that is described as applying to “a layer” may apply to adifferent layer each time that this specific step occurs). For purposesof this grammatical paragraph, “list” includes “description” or“describe”.

“3D” means three-dimensional.

Grammatical variations of defined terms shall be construed in likemanner as the defined terms. For example, if a verb is defined in oneconjugation, then other conjugations of that verb shall be construed inlike manner. Or, for example, if a noun is defined in one declension,then other declensions of that noun shall be construed in like manner.Or for example, the noun “infiltration” shall be construed in likemanner as the defined verb “infiltrate”. Or, for example, the adjective“softened” shall be construed in like manner as the defined verb“soften”.

While a preferred embodiment is disclosed, many other implementationswill occur to one of ordinary skill in the art and are all within thescope of the invention. Each of the various embodiments described abovemay be combined with other described embodiments in order to providemultiple features. Furthermore, while the foregoing describes a numberof separate embodiments of the apparatus and method of the presentinvention, what has been described herein is merely illustrative of theapplication of the principles of the present invention. Otherarrangements, methods, modifications, and substitutions by one ofordinary skill in the art are therefore also considered to be within thescope of the present invention, which is not to be limited except by theclaims that follow.

What is claimed is:
 1. A method of fabricating a three-dimensionalobject, comprising the steps of: (a) positioning powder on all or partof at least one of a plurality of substrate layers, wherein eachsubstrate layer is a sheet-like structure that is substantially planaror flat; (b) repeating step (a) for remaining layers in the plurality ofsubstrate layers; (c) folding each of the substrate layers in apredetermined order for creating the three-dimensional object; and (d)transforming at least some of the powder into a substance that flows andsubsequently hardens into hardened material, thereby binding theplurality of folded substrate layers together, wherein the hardenedmaterial is disposed in a spatial pattern that infiltrates or coats atleast one positive region in the plurality of folded substrate layersand does not substantially infiltrate or coat at least one negativeregion in the plurality of folded substrate layers, thethree-dimensional object comprising the positive regions of the stackedplurality of substrate layers that are infiltrated or coated by, andbound together by, the hardened material.
 2. The method of claim 1,further comprising the step of: (e) removing at least some of thenegative regions from the stacked folded substrate layers.
 3. The methodof claim 2, wherein step (e) is performed at least in part by mechanicalabrasion.
 4. The method of claim 1, further comprising the step of: (f)aligning the folded substrate layers in a predetermined manner forcreating the three-dimensional object, wherein the folded substratelayers are accurately aligned within the stack by an alignmentmechanism.
 5. The method of claim 1, wherein the substrate layers arecomposed of materials selected from the group consisting of carbonfibers, ceramic fibers, polymer fibers, glass fibers, and metal fibers.6. The method of claim 1, step (a) further comprising the step ofapplying a liquid on at least part of at least one of the plurality ofsubstrate layers before applying the powder such that the liquid willadhere the powder to the at least one substrate layer.
 7. The method ofclaim 1, wherein the powder is applied to substantially the entire atleast one substrate layer in step (a) and further comprising the step ofselectively removing at least some of the powder from at least a portionof the at least one substrate layer.
 8. A method of fabricating athree-dimensional object, comprising the steps of: (a) applying liquidon all or part of at least one of a plurality of substrate layers,wherein each substrate layer is a sheet-like structure that issubstantially planar or flat; (b) repeating step (a) for remaininglayers in the plurality of substrate layers; (c) positioning powder onat least part of at least one of the plurality of substrate layers,wherein at least some of the powder adheres to the previously appliedliquid; (d) folding the substrate layers in a predetermined order forcreating the three-dimensional object; and (e) transforming at leastsome of the powder into a substance that flows and subsequently hardensinto a hardened material, thereby binding the plurality of substratelayers together, wherein the hardened material is disposed in a spatialpattern that infiltrates or coats at least one positive region in theplurality of substrate layers and does not substantially infiltrate orcoat at least one negative region in the plurality of substrate layers,the three-dimensional object comprising the positive regions of thestacked plurality of substrate layers that are infiltrated or coated by,and bound together by, the hardened material.
 9. The method of claim 8,further comprising the step of: (f) removing at least some of thenegative regions from the stacked substrate layers to form thethree-dimensional object.
 10. The method of claim 9, wherein step (f) isperformed at least in part by mechanical abrasion.
 11. The method ofclaim 8, further comprising the step of: (g) aligning the foldedsubstrate layers in a predetermined manner for creating thethree-dimensional object, wherein the folded substrate layers areaccurately aligned within the stack by an alignment mechanism.
 12. Themethod of claim 8, wherein the substrate layers are composed ofmaterials selected from the group consisting of carbon fibers, ceramicfibers, polymer fibers, glass fibers, and metal fibers.
 13. The methodof claim 8, wherein the powder is applied to substantially the entire atleast one substrate layer in step (a) and further comprising the step ofselectively removing the powder from that portion of the at least onesubstrate layer to which the liquid was not applied.
 14. An apparatusfor fabricating a three-dimensional object, comprising: at least oneapplicator configured for positioning powder on all or part of aplurality of plurality of substrate layers, wherein each substrate layeris a sheet-like structure that is substantially planar or flat; foldingapparatus configured to fold each substrate layer in a predeterminedorder for creating the three-dimensional object; and at least onetransformation element configured for transforming at least some of thepowder into a substance that flows and subsequently hardens intohardened material, thereby binding at least some of the plurality offolded substrate layers together, wherein the hardened material isdisposed in a spatial pattern that infiltrates or coats at least onepositive region in the plurality of folded substrate layers and does notsubstantially infiltrate or coat at least one negative region in theplurality of folded substrate layers, the three-dimensional objectcomprising the positive regions of the stacked plurality of substratelayers that are infiltrated or coated by, and bound together by, thehardened material.
 15. The apparatus of claim 14, further comprisingsubtractive apparatus configured for removing at least some of thenegative regions from the stacked substrate layers.
 16. The apparatus ofclaim 14, further comprising at least one alignment mechanism configuredfor aligning the folded substrate layers within the stack in apredetermined manner.
 17. The apparatus of claim 14, further comprisinga liquid applicator configured to selectively deposit liquid on thepositive regions before deposition of the powder on the positiveregions.
 18. A three-dimensional article of manufacture comprising aplurality of substrate layers that are folded in a predetermined orderfor creating the article and are infiltrated or coated by, and boundtogether by, a hardened material, wherein each substrate layer is asheet-like structure that is substantially planar or flat and is madefrom materials that can be abraded, abrasively blasted, or chemicallyremoved.
 19. The article of manufacture of claim 18, wherein thesubstrate layers are made from materials selected from the groupconsisting of carbon fibers, ceramic fibers, polymer fibers, glassfibers, and metal fibers.
 20. The article of manufacture of claim 18,wherein the hardened material exhibits a set of one or morecharacteristics, which set is sufficient for distinguishing the hardenedmaterial as having formed as a result of powder having been positionedon the substrate layers and then being at least partially softenedfollowed by hardening.
 21. The article of manufacture of claim 18,wherein the substrate layers have at least one material property that isdifferent than any material property of the hardened substance